Java Archives - Sap tutorials, Salesforce tutorial, Java tutorials, Android Tutorials, Auto CAD tutorials, C, C++ tutorials, DS tutorials, Citrix tutorials, Cognos tutorials, Angular JS tutorials, Webservices tutorials, Abinito tutorials, Data mining tutorials, Data stage tutorials, Data warehouse tutorials, DBA tutorials, DBMS tutorials, .net tutorials, HTML tutorials, Hyperion tutorials, Informatica tutorials, Mainframes tutorials, Microsoft dynamics tutorials, Mobile communication tutorials, MSBI tutorials, Multimedia tutorials, Oracle tutorials, Phyton tutorials, SEO tutorials, SQL tutorials, Tableau tutorials, UNIX tutorials, VC++ tutorials, VM ware tutorials, web designing tutorials

Final keyword in Java

By tutorialkart.com 26/08/2017 Java No Comments

Java Tutorial – Final keyword in Java can be applied to a Variable, Method or Class. Java keeps restrictions on those, that are declared final.

Final keyword in Java

Final keyword in Java can be applied in the following scenarios :

Final Variable – Once a variable is declared as final, it can be initialized during declaration or in the constructor. And can never be changed during the course of the program. Hence static final variables are also called constants.
Final Method – Once a method is declared as final, it can never be overridden by any sub class that is inheriting the method’s class.
Final Class – Once a class is declared as final, it can never be inherited.

Final Keyword in Java - Java Tutorial - www.tutorialkart.com

Final Variable

Final variable once initialized can never be modified.

Following Example Java program, Audi.java, demonstrates following two scenarios :

BRAND is a final variable and initialized to “AUDI” during declaration itself and can never be changed. They remain constant for all the objects of class type Audi.
EngineNumber is only declared as final but not initialized. These kind of variables could be initialized in Constructor. They remain constant only for the object of Audi, i.e., each Audi object can have different EngineNumber.

public class Audi {
    
    public final String BRAND = "AUDI";
    public final String EngineNumber;
    
    public Audi(String EngineNumber){
        this.EngineNumber = EngineNumber;
    }
 
    public static void main(String[] args) {
        Audi audi = new Audi("ABCD1234CDEF4567");
        System.out.println("Engine Number : "+audi.EngineNumber);
        System.out.println("Car Brand : "+audi.BRAND);
    }
}

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

public class Audi {

public final String BRAND = "AUDI";

public final String EngineNumber;

public Audi(String EngineNumber){

this.EngineNumber = EngineNumber;

}

public static void main(String[] args) {

Audi audi = new Audi("ABCD1234CDEF4567");

System.out.println("Engine Number : "+audi.EngineNumber);

System.out.println("Car Brand : "+audi.BRAND);

}

Engine Number : ABCD1234CDEF4567
Car Brand : AUDI

1 2	Engine Number : ABCD1234CDEF4567 Car Brand : AUDI

Now we shall try to modify the final variable and understand what happens.

public class Audi {
	
	public final String EngineNumber;
	
	public Audi(String EngineNumber){
		this.EngineNumber = EngineNumber;
	}

	public static void main(String[] args) {
		Audi audi = new Audi("ABCD1234CDEF4567");
		audi.EngineNumber = "ERTY1234CDEF4568";
		System.out.println("Engine Number : "+audi.EngineNumber);
	}
}

1

2

3

4

5

6

7

8

9

10

11

12

13

14

public class Audi {

public final String EngineNumber;

public Audi(String EngineNumber){

this.EngineNumber = EngineNumber;

}

public static void main(String[] args) {

Audi audi = new Audi("ABCD1234CDEF4567");

audi.EngineNumber = "ERTY1234CDEF4568";

System.out.println("Engine Number : "+audi.EngineNumber);

}

Java Compiler throws an Error.

The final field Audi.EngineNumber cannot be assigned.

1	The final field Audi.EngineNumber cannot be assigned.

Final Method

Final method cannot be overridden. This property could also be used to keep restrictions in Polymorphism – Method Overriding. Let us see an Example Java Program that has Car.java and Audi.java. Audi inherits Car, and accelerate() method of car is declared final.

public class Car {

	public void brake(){
		System.out.println("break in Car");
	}
	
	public final void accelerate(){
		System.out.println("accelerate in Car");
	}
}

1

2

3

4

5

6

7

8

9

10

public class Car {

public void brake(){

System.out.println("break in Car");

}

public final void accelerate(){

System.out.println("accelerate in Car");

}

public class Audi extends Car {

	public static void main(String[] args) {
		Audi audi = new Audi();
		audi.accelerate();
		audi.brake();
	}
}

1

2

3

4

5

6

7

8

public class Audi extends Car {

public static void main(String[] args) {

Audi audi = new Audi();

audi.accelerate();

audi.brake();

}

accelerate in Car
break in Car

1 2	accelerate in Car break in Car

Now we shall try overriding accelerate method in Audi.java

public class Audi extends Car {

	public static void main(String[] args) {
		Audi audi = new Audi();
		audi.accelerate();
		audi.brake();
	}
	
	public void accelerate(){
		System.out.println("accelerate in Audi");
	}
}

1

2

3

4

5

6

7

8

9

10

11

12

public class Audi extends Car {

public static void main(String[] args) {

Audi audi = new Audi();

audi.accelerate();

audi.brake();

}

public void accelerate(){

System.out.println("accelerate in Audi");

}

Java Compilation Error occurs

Cannot override the final method from Car

1	Cannot override the final method from Car

Final Class

Final Class can never be inherited by other classes.

public final class AudiR8 {
    
    public final String BRAND = "AUDI";
    public final String EngineNumber;
    
    public AudiR8(String EngineNumber){
        this.EngineNumber = EngineNumber;
    }
 
    public static void main(String[] args) {
        AudiR8 audi = new AudiR8("ABCD1234CDEF4567");
        System.out.println("Engine Number : "+audi.EngineNumber);
        System.out.println("Car Brand : "+audi.BRAND);
    }
}

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

public final class AudiR8 {

public final String BRAND = "AUDI";

public final String EngineNumber;

public AudiR8(String EngineNumber){

this.EngineNumber = EngineNumber;

}

public static void main(String[] args) {

AudiR8 audi = new AudiR8("ABCD1234CDEF4567");

System.out.println("Engine Number : "+audi.EngineNumber);

System.out.println("Car Brand : "+audi.BRAND);

}

Engine Number : ABCD1234CDEF4567
Car Brand : AUDI

1 2	Engine Number : ABCD1234CDEF4567 Car Brand : AUDI

We shall now try to extend this AudiR8.java from another class and understand what happens

public class AnotherCar extends AudiR8 { }

1	public class AnotherCar extends AudiR8 { }

Java Compiler throws Error : The type AnotherCar cannot subclass the final class AudiR8

Conclusion :

In this Java Tutorial, we have learnt about final keyword in Java that can be applied to a Variable, Method or Class and also the restrictions Java keeps on those, that are declared final. In our next tutorial, we shall learn about another Object Oriented Concept – Abstraction in Java.

Method Overriding in Java

By tutorialkart.com 26/08/2017 Java No Comments

In this tutorial, we shall learn Overriding in Java with Example Programs, where methods of Super Class are overridden by methods of Sub Class.

Method Overriding in Java

Method Overriding is a way to realize Polymorphism in Java.

In context of Sub Class extending a Super Class, the Sub Class can access super class’s methods. If in case the Sub Class wants functionality of an existing method in Super Class to be replaced by some specific implementation, then Java provides the ability to override the existing functionality through Method Overriding. It can also be thought of as Runtime Polymorphism.

Following are the rules for implementing Method Overriding in Java:

The method declaration should be same as that of the method that is to be overridden.
The class (sub class) should extend another class (super class), prior to even try overriding.
Sub Class can never override final methods of Super Class.

We shall take an example scenario where Car is a Super Class and Audi is a Sub Class.

public class Car {

	public void brake(){
		System.out.println("break in Car");
	}
	
	public void accelerate(){
		System.out.println("accelerate in Car");
	}
}

1

2

3

4

5

6

7

8

9

10

public class Car {

public void brake(){

System.out.println("break in Car");

}

public void accelerate(){

System.out.println("accelerate in Car");

}

public class Audi extends Car {

	public static void main(String[] args) {
		Audi audi = new Audi();
		audi.accelerate();
		audi.brake();
	}
}

1

2

3

4

5

6

7

8

public class Audi extends Car {

public static void main(String[] args) {

Audi audi = new Audi();

audi.accelerate();

audi.brake();

}

accelerate in Car
break in Car

1 2	accelerate in Car break in Car

Sub Class Overriding Method of Super Class

Now we shall override accelerate method in Audi.java by overriding accelerate() in Car.java

public class Car {

	public void brake(){
		System.out.println("break in Car");
	}
	
	public void accelerate(){
		System.out.println("accelerate in Car");
	}
}

1

2

3

4

5

6

7

8

9

10

public class Car {

public void brake(){

System.out.println("break in Car");

}

public void accelerate(){

System.out.println("accelerate in Car");

}

public class Audi extends Car {

	public static void main(String[] args) {
		Audi audi = new Audi();
		audi.accelerate();
		audi.brake();
	}
	
	public void accelerate(){
		System.out.println("accelerate in Audi");
	}
}

1

2

3

4

5

6

7

8

9

10

11

12

public class Audi extends Car {

public static void main(String[] args) {

Audi audi = new Audi();

audi.accelerate();

audi.brake();

}

public void accelerate(){

System.out.println("accelerate in Audi");

}

accelerate in Audi
break in Car

1 2	accelerate in Audi break in Car

What happens when you try to override final method of Super Class

Any method that is declared final in the Super Class cannot be overridden by Sub Class. If you try doing so, you may get an Error as shown in the following :

public class Car {

	public void brake(){
		System.out.println("break in Car");
	}
	
	public final void accelerate(){
		System.out.println("accelerate in Car");
	}
}

1

2

3

4

5

6

7

8

9

10

public class Car {

public void brake(){

System.out.println("break in Car");

}

public final void accelerate(){

System.out.println("accelerate in Car");

}

public class Audi extends Car {

	public static void main(String[] args) {
		Audi audi = new Audi();
		audi.accelerate();
		audi.brake();
	}
	
	public void accelerate(){
		System.out.println("accelerate in Audi");
	}
}

1

2

3

4

5

6

7

8

9

10

11

12

public class Audi extends Car {

public static void main(String[] args) {

Audi audi = new Audi();

audi.accelerate();

audi.brake();

}

public void accelerate(){

System.out.println("accelerate in Audi");

}

Error: A JNI error has occurred, please check your installation and try again
Exception in thread "main" java.lang.VerifyError: class Audi overrides final method accelerate.()V
	at java.lang.ClassLoader.defineClass1(Native Method)
	at java.lang.ClassLoader.defineClass(ClassLoader.java:763)
	at java.security.SecureClassLoader.defineClass(SecureClassLoader.java:142)

1

2

3

4

5

Error: A JNI error has occurred, please check your installation and try again

Exception in thread "main" java.lang.VerifyError: class Audi overrides final method accelerate.()V

at java.lang.ClassLoader.defineClass1(Native Method)

at java.lang.ClassLoader.defineClass(ClassLoader.java:763)

at java.security.SecureClassLoader.defineClass(SecureClassLoader.java:142)

Conclusion :

In this Java Tutorial, we have learnt Method Overriding in Java with Example Programs, the prerequisites to Override a method. In our next tutorial, we shall learn about Final Keyword in Java.

Method Overloading in Java

By tutorialkart.com 26/08/2017 Java No Comments

Java Tutorial – We shall learn about Overloading in Java, ability to use same name for different methods with different set of arguments, with Java Example Programs.

Overloading in Java

Overloading is a way to realize Polymorphism in Java.

If a method can expect different types of inputs for the same functionality it implements, implementing different methods (with different method names) for each scenario may complicate the readability of code.

For example, we need a functionality to add two numbers. Now these two numbers could be integer values, float values, long values or double values. If we implement methods like addTwoInts(int a, int b), addTwoFloats(float a, float b), addIntFloat(int a, float b), etc., it becomes very difficult to use these methods in other classes because of lack of readability. Java provides the ability to overload a method based on the nature of parameters passed in the function call, provided the methods have a same name.

How to implement Overloading in Java

Following are the rules to implement Overloading of methods :

All the methods that take park in Overloading should have the same name.
No two methods should have the same set of arguments. They should differ either in
- the number of arguments they have in their definition or
- the type of arguments they have in their definition

If a method is not found for a set of arguments, the compiler does Type Promotion and checks for a suitable method definition. We shall learn in detail about Type Promotion with an example in due course of this tutorial.

Note : Different Return types do not make two methods different with respect to Overloading in Java.

Example of Overloading in Java

We shall use the same example of addition to demonstrate Overloading in Java

/**
 * Example program to demonstrate Overloading in Java 
 */
public class Calculation {

	public static void main(String[] args) {
		Calculation calc = new Calculation();
		System.out.println(calc.add(4, 8));	// add(int a, int b) is loaded 
		System.out.println(calc.add(4, 8.5));	// add(int a, float b)  is loaded
		System.out.println(calc.add("25", "85"));	// add(String a, String b) is loaded
		System.out.println(calc.add(25, 88888888888888888888888.0));	// add(int a, double b) is loaded
		System.out.println(calc.add(25));	// add(int a) is loaded
	}
	
	public int add(int a, int b){
		System.out.println("add(int a, int b) is called");
		return a+b;
	}
	
	public int add(String a, String b){
		System.out.println("add(String a, String b) is called");
		return Integer.parseInt(a)+Integer.parseInt(b);
	}
	
	public float add(int a, float b){
		System.out.println("add(int a, float b) is called");
		return a+b;
	}
	
	public double add(int a, double b){
		System.out.println("add(int a, double b) is called");
		return a+b;
	}
	
	public int add(int a){
		System.out.println("add(int a) is called");
		return a+1;
	}
}

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

20

21

22

23

24

25

26

27

28

29

30

31

32

33

34

35

36

37

38

39

/**

* Example program to demonstrate Overloading in Java

*/

public class Calculation {

public static void main(String[] args) {

Calculation calc = new Calculation();

System.out.println(calc.add(4, 8)); // add(int a, int b) is loaded

System.out.println(calc.add(4, 8.5)); // add(int a, float b) is loaded

System.out.println(calc.add("25", "85")); // add(String a, String b) is loaded

System.out.println(calc.add(25, 88888888888888888888888.0)); // add(int a, double b) is loaded

System.out.println(calc.add(25)); // add(int a) is loaded

}

public int add(int a, int b){

System.out.println("add(int a, int b) is called");

return a+b;

}

public int add(String a, String b){

System.out.println("add(String a, String b) is called");

return Integer.parseInt(a)+Integer.parseInt(b);

}

public float add(int a, float b){

System.out.println("add(int a, float b) is called");

return a+b;

}

public double add(int a, double b){

System.out.println("add(int a, double b) is called");

return a+b;

}

public int add(int a){

System.out.println("add(int a) is called");

return a+1;

}

add(int a, int b) is called
12
add(int a, double b) is called
12.5
add(String a, String b) is called
110
add(int a, double b) is called
8.888888888888889E22
add(int a) is called
26

1

2

3

4

5

6

7

8

9

10

add(int a, int b) is called

12

add(int a, double b) is called

12.5

add(String a, String b) is called

110

add(int a, double b) is called

8.888888888888889E22

add(int a) is called

26

Now we shall cross verify the rules that we already stated with the above program.

All the five methods that take part in overloading have same method name “add”.
No two definitions of add function have same set of arguments. One add method have (int, int), another has (int, float), etc.

Type promotion during method Overloading

If a method is not found for a set of arguments, the compiler does Type Promotion and checks for a suitable method definition. Following diagram shows different type promotions that are possible.

Overloading in Java - Java Tutorial - www.tutorialkart.com

If there is forward path between two data types, then the starting datatype in the path can be type promoted to the datatype at end of the path.

byte can be type promoted to short.
short can be type promoted to int.
Implication can be applied in type promotion. i.e., if byte can be promoted to short and short can be promoted to int, then byte can be promoted to int. Also byte can be promoted to long, double or float.

We shall use the same Calculation class, but remove the definition add(int, int). As we have add(int, float), even we make a call add(int, int), as int can be promoted to float, double or long, we have add(int, float) and add(int, double) which are potential overloadable methods.

/**
 * Example program to demonstrate Overloading in Java with Type Promotion
 */
public class Calculation {

	public static void main(String[] args) {
		Calculation calc = new Calculation();
		System.out.println(calc.add(4, 8));
		System.out.println(calc.add(4, 8.5));
		System.out.println(calc.add("25", "85"));
		System.out.println(calc.add(25, 88888888888888888888888.0));
		System.out.println(calc.add(25));
	}
	
	public int add(String a, String b){
		System.out.println("add(String a, String b) is called");
		return Integer.parseInt(a)+Integer.parseInt(b);
	}
	
	public float add(int a, float b){
		System.out.println("add(int a, float b) is called");
		return a+b;
	}
	
	public double add(int a, double b){
		System.out.println("add(int a, double b) is called");
		return a+b;
	}
	
	public int add(int a){
		System.out.println("add(int a) is called");
		return a+1;
	}
}

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

20

21

22

23

24

25

26

27

28

29

30

31

32

33

34

/**

* Example program to demonstrate Overloading in Java with Type Promotion

*/

public class Calculation {

public static void main(String[] args) {

Calculation calc = new Calculation();

System.out.println(calc.add(4, 8));

System.out.println(calc.add(4, 8.5));

System.out.println(calc.add("25", "85"));

System.out.println(calc.add(25, 88888888888888888888888.0));

System.out.println(calc.add(25));

}

public int add(String a, String b){

System.out.println("add(String a, String b) is called");

return Integer.parseInt(a)+Integer.parseInt(b);

}

public float add(int a, float b){

System.out.println("add(int a, float b) is called");

return a+b;

}

public double add(int a, double b){

System.out.println("add(int a, double b) is called");

return a+b;

}

public int add(int a){

System.out.println("add(int a) is called");

return a+1;

}

add(int a, float b) is called
12.0
add(int a, double b) is called
12.5
add(String a, String b) is called
110
add(int a, double b) is called
8.888888888888889E22
add(int a) is called
26

1

2

3

4

5

6

7

8

9

10

add(int a, float b) is called

12.0

add(int a, double b) is called

12.5

add(String a, String b) is called

110

add(int a, double b) is called

8.888888888888889E22

add(int a) is called

26

Int has been promoted to Float.

Now, we shall remove add(int, float) and see the result.

/**
 * Example program to demonstrate Overloading in Java 
 */
public class Calculation {

	public static void main(String[] args) {
		Calculation calc = new Calculation();
		System.out.println(calc.add(4, 8));
		System.out.println(calc.add(4, 8.5));
		System.out.println(calc.add("25", "85"));
		System.out.println(calc.add(25, 88888888888888888888888.0));
		System.out.println(calc.add(25));
	}
	
	public int add(String a, String b){
		System.out.println("add(String a, String b) is called");
		return Integer.parseInt(a)+Integer.parseInt(b);
	}
	
	public double add(int a, double b){
		System.out.println("add(int a, double b) is called");
		return a+b;
	}
	
	public int add(int a){
		System.out.println("add(int a) is called");
		return a+1;
	}
}

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

20

21

22

23

24

25

26

27

28

29

/**

* Example program to demonstrate Overloading in Java

*/

public class Calculation {

public static void main(String[] args) {

Calculation calc = new Calculation();

System.out.println(calc.add(4, 8));

System.out.println(calc.add(4, 8.5));

System.out.println(calc.add("25", "85"));

System.out.println(calc.add(25, 88888888888888888888888.0));

System.out.println(calc.add(25));

}

public int add(String a, String b){

System.out.println("add(String a, String b) is called");

return Integer.parseInt(a)+Integer.parseInt(b);

}

public double add(int a, double b){

System.out.println("add(int a, double b) is called");

return a+b;

}

public int add(int a){

System.out.println("add(int a) is called");

return a+1;

}

add(int a, double b) is called
12.0
add(int a, double b) is called
12.5
add(String a, String b) is called
110
add(int a, double b) is called
8.888888888888889E22
add(int a) is called
26

1

2

3

4

5

6

7

8

9

10

add(int a, double b) is called

12.0

add(int a, double b) is called

12.5

add(String a, String b) is called

110

add(int a, double b) is called

8.888888888888889E22

add(int a) is called

26

For both add(int, int) and add(int, float), add(int, double) has been called i.e., int and float are promoted to double.
You may experiment with other type promotions and verify the results with the type promotions presented in the picture.

Conclusion :

In this Java Tutorial, we have learnt about Overloading in Java with an Example program of adding two numbers for different set of input arguments and also type promotions that are possible with different data types in Java for overloading methods. In our next tutorial, we shall learn about Overriding in Java.

How to reverse a String in Java ?

By tutorialkart.com 08/05/2017 Java No Comments

Java Tutorial – We shall learn how to reverse a String in Java Programming Language.

Reverse a String in Java

We shall get the bytes of given String and order them in reverse fashion.

Following is the Java Example to reverse a String :

/**
 * Java Example Program, to reverse a String in Java
 */

public class ReverseString {

	public static void main(String[] args) {
		String str = "www.tutorialkart.com";
		String reverseStr="";
		
		for(byte c:str.getBytes()){
			reverseStr=(char)c+reverseStr;
		}
		System.out.println("Original String is : "+str);
		System.out.println("Reversed String is : "+reverseStr);
	}
}

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

/**

* Java Example Program, to reverse a String in Java

*/

public class ReverseString {

public static void main(String[] args) {

String str = "www.tutorialkart.com";

String reverseStr="";

for(byte c:str.getBytes()){

reverseStr=(char)c+reverseStr;

}

System.out.println("Original String is : "+str);

System.out.println("Reversed String is : "+reverseStr);

}

When the above program is run, output to the console is as shown in the following :

Original String is : www.tutorialkart.com
Reversed String is : moc.traklairotut.www

1 2	Original String is : www.tutorialkart.com Reversed String is : moc.traklairotut.www

Conclusion :

In this Java Tutorial, we have learnt how to reverse a given String in Java.

Following are some of the other Java String Examples :

Replace all occurrences of a substring with another in a string using Java

By tutorialkart.com 08/05/2017 Java No Comments

In this Java Tutorial, we shall see how to use String.replaceAll(String subString, String otherString) method to replace all occurrences of a substring with another in a string using Java.

Replace all occurrences of a substring with another in a string using Java

Following is the Java Example program to replace all occurrences of a substring with another in a string using Java.

/**
 * Java Example Program, to replace all occurrences of a substring with another in a string using Java
 */

public class ReplaceAllOccurrences {

	public static void main(String[] args) {
		String str = "Hi! Good morning. Have a Good day.";
		String subStr = "Good";
		String otherStr = "Very-Good";
		
		String resultStr = str.replaceAll(subStr, otherStr);
		System.out.println("Original-String : "+str);
		System.out.println("substring : "+subStr);
		System.out.println("Other-String : "+otherStr);
		System.out.println("After replacement of all occurrences of substring by Other-String in Original-String : \n"+resultStr);
	}
}

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

/**

* Java Example Program, to replace all occurrences of a substring with another in a string using Java

*/

public class ReplaceAllOccurrences {

public static void main(String[] args) {

String str = "Hi! Good morning. Have a Good day.";

String subStr = "Good";

String otherStr = "Very-Good";

String resultStr = str.replaceAll(subStr, otherStr);

System.out.println("Original-String : "+str);

System.out.println("substring : "+subStr);

System.out.println("Other-String : "+otherStr);

System.out.println("After replacement of all occurrences of substring by Other-String in Original-String : \n"+resultStr);

}

When the above program is run, the output to the console is as shown in the following :

Original-String : Hi! Good morning. Have a Good day.
substring : Good
Other-String : Very-Good
After replacement of all occurrences of substring by Other-String in Original-String : 
Hi! Very-Good morning. Have a Very-Good day.

1

2

3

4

5

Original-String : Hi! Good morning. Have a Good day.

substring : Good

Other-String : Very-Good

After replacement of all occurrences of substring by Other-String in Original-String :

Hi! Very-Good morning. Have a Very-Good day.

Conclusion :

In this Java Tutorial, we have learnt how to replace all occurrences of a substring with another in a string.

Following are some of the other Java String Examples :

How to get the index of first occurrence of a substring in a String using Java ?

By tutorialkart.com 08/05/2017 Java No Comments

In this Java Tutorial, we shall learn to get the index of first occurrence of a substring in a String using Java Programming Language.

Get the index of first occurrence of a substring in a String using Java ?

We shall make use of String.indexOf(String otherString) method, to find the index of first occurrence of a substring. If the substring is present in the string, it returns the index of its first occurrence, else it returns -1 indicating that the substring specified is not present in the string.

Following the Java Example to get the index of first occurrence of a substring

/**
 * Java Example program to find the index of first occurrence of a substring in a string
 */
public class FirstOccuranceExample {

	public static void main(String[] args) {
		String str1 = "helloworldgoodmorning";
		String str2 = "good";
		// str1.indexOf(str2) method returns the index of first occurrence of str2 in str1
		int indexOfSubStr = str1.indexOf(str2);
		
		System.out.println("The substring first appeared in the string at index : "+ indexOfSubStr);
	}
}

1

2

3

4

5

6

7

8

9

10

11

12

13

14

/**

* Java Example program to find the index of first occurrence of a substring in a string

*/

public class FirstOccuranceExample {

public static void main(String[] args) {

String str1 = "helloworldgoodmorning";

String str2 = "good";

// str1.indexOf(str2) method returns the index of first occurrence of str2 in str1

int indexOfSubStr = str1.indexOf(str2);

System.out.println("The substring first appeared in the string at index : "+ indexOfSubStr);

}

When the above program is run, the output to the console is as shown below :

The substring first appeared in the string at index : 10

1	The substring first appeared in the string at index : 10

Following is the Java Example to get the index of first occurrence of a substring in string, reading both the strings from console input

import java.util.Scanner;

/**
 * An example java program to find the index of first occurrence of a substring in a string
 */
public class PrintString {

	public static void main(String[] args) {
		Scanner scanner = new Scanner(System. in);
		System.out.print("Enter a string : ");
		String str1 = scanner.nextLine();
		System.out.print("Enter the substring : ");
		String str2 = scanner.nextLine();
		// str1.indexOf(str2) method returns the index of first occurrence of str2 in str1characters as that of str2
		int indexOfSubStr = str1.indexOf(str2);
		
		System.out.println("The substring appeared in the string at index : "+ indexOfSubStr);
	}
}

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

import java.util.Scanner;

/**

* An example java program to find the index of first occurrence of a substring in a string

*/

public class PrintString {

public static void main(String[] args) {

Scanner scanner = new Scanner(System. in);

System.out.print("Enter a string : ");

String str1 = scanner.nextLine();

System.out.print("Enter the substring : ");

String str2 = scanner.nextLine();

// str1.indexOf(str2) method returns the index of first occurrence of str2 in str1characters as that of str2

int indexOfSubStr = str1.indexOf(str2);

System.out.println("The substring appeared in the string at index : "+ indexOfSubStr);

}

When the above program is run, the output to the console is as shown below :

Enter a string : good morning
Enter the substring : morning
The substring appeared in the string at index : 5

1

2

3

Enter a string : good morning

Enter the substring : morning

The substring appeared in the string at index : 5

Conclusion :

In this Java Tutorial, we have learnt how to get index of first occurrence of a substring in a String using Java Programming Language.

Following are some of the other Java String Examples :

How to check if two Strings are Equal in Java ?

By tutorialkart.com 08/05/2017 Java No Comments

In this Java Tutorial, we shall see how to check if two Strings are Equal in Java using the method String.equals(String anotherString). Also, we shall see a program to ignore the case, and check if two Strings are Equal.

Java Example program to check if two Strings are Equal

/**
 * An example java program to compare if two strings are equal
 */
public class CheckStringsEqual {

	public static void main(String[] args) {
		// string declaration
		String str1 = "Hello World";
		String str2 = "Hello World";
		// str1.equals(str2) method returns true if str1 has same characters as that of str2
		boolean areTwoStringsEqual = str1.equals(str2);
		
		if(areTwoStringsEqual){
			System.out.print("The two strings are equal.");
		} else{
			System.out.print("The two strings are not equal.");
		}
	}
}

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

/**

* An example java program to compare if two strings are equal

*/

public class CheckStringsEqual {

public static void main(String[] args) {

// string declaration

String str1 = "Hello World";

String str2 = "Hello World";

// str1.equals(str2) method returns true if str1 has same characters as that of str2

boolean areTwoStringsEqual = str1.equals(str2);

if(areTwoStringsEqual){

System.out.print("The two strings are equal.");

} else{

System.out.print("The two strings are not equal.");

}

When the program is run, the output to the console is as shown in the following :

The two strings are equal.

1	The two strings are equal.

Java Example program to check if two Strings are Equal, with input strings read from console

import java.util.Scanner;

/**
 * An example java program to compare if two strings are equal, with inputs read from console
 */
public class CheckStringsEqual {

	public static void main(String[] args) {
		Scanner scanner = new Scanner(System. in);
		// string declaration
		System.out.print("Enter first string : ");
		String str1 = scanner.nextLine();
		System.out.print("Enter second string : ");
		String str2 = scanner.nextLine();
		// str1.equals(str2) method returns true if str1 has same characters as that of str2
		boolean areTwoStringsEqual = str1.equals(str2);
		
		if(areTwoStringsEqual){
			System.out.print("The two strings are equal.");
		} else{
			System.out.print("The two strings are not equal.");
		}
	}
}

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

20

21

22

23

24

import java.util.Scanner;

/**

* An example java program to compare if two strings are equal, with inputs read from console

*/

public class CheckStringsEqual {

public static void main(String[] args) {

Scanner scanner = new Scanner(System. in);

// string declaration

System.out.print("Enter first string : ");

String str1 = scanner.nextLine();

System.out.print("Enter second string : ");

String str2 = scanner.nextLine();

// str1.equals(str2) method returns true if str1 has same characters as that of str2

boolean areTwoStringsEqual = str1.equals(str2);

if(areTwoStringsEqual){

System.out.print("The two strings are equal.");

} else{

System.out.print("The two strings are not equal.");

}

When the program is run, the output to the console is as shown in the following :

Enter first string : good morning
Enter second string : good morning
The two strings are equal.

1

2

3

Enter first string : good morning

Enter second string : good morning

The two strings are equal.

Java Example program to ignore the case of characters in the Strings and check if two Strings are Equal

/**
 * An example java program to ignore case and compare if two strings are equal
 */
public class CheckStringsEqual {

	public static void main(String[] args) {
		// string declaration
		String str1 = "Hello World";
		String str2 = "hello world";
		// str1.equals(str2) method returns true if str1 has same characters as that of str2
		boolean areTwoStringsEqual = str1.equalsIgnoreCase(str2);
		
		if(areTwoStringsEqual){
			System.out.print("The two strings are equal.");
		} else{
			System.out.print("The two strings are not equal.");
		}
	}
}

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

/**

* An example java program to ignore case and compare if two strings are equal

*/

public class CheckStringsEqual {

public static void main(String[] args) {

// string declaration

String str1 = "Hello World";

String str2 = "hello world";

// str1.equals(str2) method returns true if str1 has same characters as that of str2

boolean areTwoStringsEqual = str1.equalsIgnoreCase(str2);

if(areTwoStringsEqual){

System.out.print("The two strings are equal.");

} else{

System.out.print("The two strings are not equal.");

}

When the program is run, the output to the console is as shown in the following :

The two strings are equal.

1	The two strings are equal.

Java Example program to ignore the case of characters in the Strings and check if two Strings are Equal, with input strings read from console

import java.util.Scanner;

/**
 * An example java program to ignore case and compare if two strings are equal, with inputs read from console
 */
public class CheckStringsEqual {

	public static void main(String[] args) {
		Scanner scanner = new Scanner(System. in);
		// string declaration
		System.out.print("Enter first string : ");
		String str1 = scanner.nextLine();
		System.out.print("Enter second string : ");
		String str2 = scanner.nextLine();
		// str1.equals(str2) method returns true if str1 has same characters as that of str2
		boolean areTwoStringsEqual = str1.equalsIgnoreCase(str2);
		
		if(areTwoStringsEqual){
			System.out.print("The two strings are equal.");
		} else{
			System.out.print("The two strings are not equal.");
		}
	}
}

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

20

21

22

23

24

import java.util.Scanner;

/**

* An example java program to ignore case and compare if two strings are equal, with inputs read from console

*/

public class CheckStringsEqual {

public static void main(String[] args) {

Scanner scanner = new Scanner(System. in);

// string declaration

System.out.print("Enter first string : ");

String str1 = scanner.nextLine();

System.out.print("Enter second string : ");

String str2 = scanner.nextLine();

// str1.equals(str2) method returns true if str1 has same characters as that of str2

boolean areTwoStringsEqual = str1.equalsIgnoreCase(str2);

if(areTwoStringsEqual){

System.out.print("The two strings are equal.");

} else{

System.out.print("The two strings are not equal.");

}

When the program is run, the output to the console is as shown in the following :

Enter first string : good MORNing
Enter second string : good morning
The two strings are equal.

1

2

3

Enter first string : good MORNing

Enter second string : good morning

The two strings are equal.

Conclusion :

In this Java Tutorial, we have learned to check if two strings are equal in Java, with inputs given directly in the program or read from the console, and ignoring the case of characters in the string if necessary.

Following are some of the other Java String Examples :

How to read a String from console input in Java ?

By tutorialkart.com 06/05/2017 Java No Comments

Read a String from console input in Java

In this Java Tutorial, we shall use Scanner scanner = new Scanner(System. in); to read a String from console input in Java.

import java.util.Scanner;

/**
 * An example program to read a String from console input in Java
 */
public class ReadString {

	public static void main(String[] args) {
		System.out.print("Enter a string : ");
		Scanner scanner = new Scanner(System. in);
		String inputString = scanner. nextLine();
		System.out.println("String read from console is : \n"+inputString);
	}
}

1

2

3

4

5

6

7

8

9

10

11

12

13

14

import java.util.Scanner;

/**

* An example program to read a String from console input in Java

*/

public class ReadString {

public static void main(String[] args) {

System.out.print("Enter a string : ");

Scanner scanner = new Scanner(System. in);

String inputString = scanner. nextLine();

System.out.println("String read from console is : \n"+inputString);

}

When the program is run, the execution waits after printing “Enter a string : “, where you would enter a string like “hello world”. The program prints the string read from the console input in the next step. The whole output in the console would be as shown in the following :

Enter a string : hello world
String read from console is : 
hello world

1

2

3

Enter a string : hello world

String read from console is :

hello world

System.in

In the context of reading something from console, System class provides a means to access standard input through one of its fields, in. ‘in’ field is a Stream (to be specific, its a InputStream), which is declared public static and final. Hence, one can use ‘in’ directly without any initialization.Typically this InputStream corresponds to keyboard input or another input source specified by the host environment or user.

Conclusion :

In this Java Tutorial, we have learnt to use Scanner scanner = new Scanner(System. in); to read a String from console input in Java.

Category: Java

Final keyword in Java

Final Variable

Final Method

Final Class

Conclusion :

Method Overriding in Java

Sub Class Overriding Method of Super Class

What happens when you try to override final method of Super Class

Conclusion :

Overloading in Java

How to implement Overloading in Java

Example of Overloading in Java

Type promotion during method Overloading

Conclusion :

Reverse a String in Java

Conclusion :

Following are some of the other Java String Examples :

Replace all occurrences of a substring with another in a string using Java

Conclusion :

Following are some of the other Java String Examples :

Get the index of first occurrence of a substring in a String using Java ?

Following the Java Example to get the index of first occurrence of a substring

Following is the Java Example to get the index of first occurrence of a substring in string, reading both the strings from console input

Conclusion :

Following are some of the other Java String Examples :

Java Example program to check if two Strings are Equal

Java Example program to check if two Strings are Equal, with input strings read from console

Java Example program to ignore the case of characters in the Strings and check if two Strings are Equal

Java Example program to ignore the case of characters in the Strings and check if two Strings are Equal, with input strings read from console

Conclusion :

Following are some of the other Java String Examples :

Read a String from console input in Java

System.in

Conclusion :

Following are some of the other Java String Examples :