Java StringBuilder.substring() – Syntax & Examples

Java StringBuilder.substring() – Examples

In this tutorial, we will learn about the Java StringBuilder.substring() function, and learn how to use this function with the help of examples.

substring(int start)

StringBuilder.substring() returns a new String that contains a subsequence of characters, formed using start position and an optional end position, contained in this character sequence.

Syntax

The syntax of substring() function is

substring(int start)

where

Parameter	Description
start	Integer representing the start position of substring in StringBuilder.

Returns

The function returns String object.

Example 1 – substring(int start)

In this example, we will create a StringBuilder object and initialize with some string passed as argument.

We will then get the sub-string from the StringBuilder using substring() method from starting position of 5 in the character sequence of StringBuilder.

Java Program

class Example { 
    public static void main(String[] args) { 
        // create a StringBuilder object 
        // with a String pass as parameter 
        StringBuilder stringBuilder = new StringBuilder("abcdefghijkl"); 
   
        // print string 
        System.out.println("Original String: "+stringBuilder); 
   
        // get substring start from index 5 
        // using substring() and print results 
        System.out.println("Sub String     : "+ stringBuilder.substring(5)); 
    } 
}

Output

Original String: abcdefghijkl
Sub String     : fghijkl

Example 2 – substring(int start)

In this example, we will test a negative scenario where substring() throws java.lang.StringIndexOutOfBoundsException. We will give an index that is out of range for the sequence in StringBuilder.

Java Program

class Example { 
    public static void main(String[] args) { 
        // create a StringBuilder object 
        // with a String pass as parameter 
        StringBuilder str = new StringBuilder("abcdefghijklm"); 
   
        try { 
            // get substring starts from index -7 
            str.substring(-7); 
        } 
   
        catch (Exception e) { 
            System.out.println("Exception: " + e); 
        } 
    } 
}

Output

Exception: java.lang.StringIndexOutOfBoundsException: start -7, end 13, length 13

substring(int start, int end)

StringBuilder.substring() returns a new String that contains a subsequence of characters currently contained in this sequence, whose starting and ending are provided as arguments.

Syntax

The syntax of substring() function is

substring(int start, int end)

where

Parameter	Description
start	Integer representing the start position of substring in StringBuilder.
end	Integer representing the end position of substring in StringBuilder.

Returns

The function returns String object.

Example 3 – substring(int start, int end)

In this example, we will create a StringBuilder object and initialize with some string passed as argument.

We will then get the sub-string from the StringBuilder using substring() method from starting position of 5 and ending position of 8 in the character sequence of StringBuilder

Java Program

class Example { 
    public static void main(String[] args) { 
        StringBuilder stringBuilder = new StringBuilder("abcdefghijklmn"); 
   
        // print string 
        System.out.println("Original String : " + stringBuilder); 
   
        // get substring start from index 5 to index 8 
        // using substring() and print results 
        System.out.println("Sub String      : "+ stringBuilder.substring(5, 8)); 
    } 
}

Output

Original String : abcdefghijklmn
Sub String      : fgh

Example 4 – substring(int start, int end)

In this example, we will test a negative scenario where substring() throws java.lang.StringIndexOutOfBoundsException. We will give a value for start parameter such that it is greater than end.

Java Program

class Example { 
    public static void main(String[] args) { 
        StringBuilder stringBuilder = new StringBuilder("abcdefghijkl"); 
        System.out.println("Original String: "+stringBuilder); 
        System.out.println("Sub String     : "+ stringBuilder.substring(8, 2)); 
    } 
}

Output

Original String: abcdefghijkl
Exception in thread "main" java.lang.StringIndexOutOfBoundsException: start 8, end 2, length 12
    at java.base/java.lang.AbstractStringBuilder.checkRangeSIOOBE(Unknown Source)
    at java.base/java.lang.AbstractStringBuilder.substring(Unknown Source)
    at java.base/java.lang.StringBuilder.substring(Unknown Source)
    at Example.main(Example.java:12)

Conclusion

In this Java Tutorial, we have learnt the syntax of Java StringBuilder.substring() function, and also learnt how to use this function with the help of examples.