In Java, the String class provides the subSequence() method. This subSequence() method extracts a portion of a string as a CharSequence. This method is useful for retrieving specific character ranges from a string which enhances string manipulation.

In this article, we will learn how to use the subSequence() method in Java with practical examples.

Example:

Below is the basic example to demonstrate the working of the String.subSequence() function.

// Java Program to demonstrate the working of 
// String.subSequence() method

import java.lang.Math;

class SubSequence {

    public static void main(String args[]) {

        String s = "Programming";

        // Extracting substring from index 7 to 11 (exclusive)
        CharSequence sub = s.subSequence(7, 11);

        System.out.println("" + sub);
    }
}

// Java Program to demonstrate the working of 

// String.subSequence() method

​

import java.lang.Math;

​

class SubSequence {

​

    public static void main(String args[]) {

​

        String s = "Programming";

​

        // Extracting substring from index 7 to 11 (exclusive)

        CharSequence sub = s.subSequence(7, 11);

​

        System.out.println("" + sub);

    }

}

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Syntax of subSequence() Method

CharSequence subSequence(int start, int end);

Parameters:

• start: This is the index from where the subsequence starts, it is inclusive.
• end: This is the index where the subsequence ends, it is exclusive.

Returns Value: It returns the specified subsequence in range [start, end).

Errors and Exceptions: IndexOutOfBoundsException: It throws this error if start or end are negative, if end is greater than length(), or if start is greater than end.

Other Ways to Use Java String.subSequence() Method

Here, we will learn some other practical examples demonstrating the usage of the Java String.subSequence() method.

1. Using subSequence() with Different Indices

This extracts a portion of the string by specifying a custom starting and ending index. It excludes the character at the end index.

Example:

// Java Program to demonstrate the usage of 
// subSequence() method with different indices

public class SubSequence {
  
    public static void main(String[] args) {
      
        String s = "Programming";

        // Extracting substring from index 3 to 6 (exclusive)
        CharSequence sub = s.subSequence(3, 7);

        System.out.println("" + sub);  
    }
}

// Java Program to demonstrate the usage of 

// subSequence() method with different indices

​

public class SubSequence {

    public static void main(String[] args) {

        String s = "Programming";

​

        // Extracting substring from index 3 to 6 (exclusive)

        CharSequence sub = s.subSequence(3, 7);

​

        System.out.println("" + sub);  

    }

}

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Explanation: The subSequence(3, 7) extracts characters starting from index 3 and ending at index 6 (index 7 is exclusive).

2. Using subSequence() with a Full Range

This extracts a sequence of characters from the entire string by providing indices from 0 to the string length.

Example:

// Java Program to demonstrate extracting the full string 
// using subSequence() method

public class SubSequence {
  
    public static void main(String[] args) {
      
        String s = "Programming";

        // Extracting the full string
        CharSequence sub = s.subSequence(0, s.length());

        System.out.println("" + sub); 
    }
}

// Java Program to demonstrate extracting the full string 

// using subSequence() method

​

public class SubSequence {

    public static void main(String[] args) {

        String s = "Programming";

​

        // Extracting the full string

        CharSequence sub = s.subSequence(0, s.length());

​

        System.out.println("" + sub); 

    }

}

Programming

3. Handling Index Out of Bounds

When the provided indices are invalid, for example, start is greater than end or indices are out of range, it throws a StringIndexOutOfBoundsException.

Example:

public class SubSequence {
  
    public static void main(String[] args) {
      
        String s = "Programming";

        try {
            // Extracting using an invalid range
            CharSequence sub = s.subSequence(2, 20);
            System.out.println("" + sub);
        } catch (IndexOutOfBoundsException e) {
            System.out.println("Error: " + e); 
        }
    }
}

public class SubSequence {

    public static void main(String[] args) {

        String s = "Programming";

​

        try {

            // Extracting using an invalid range

            CharSequence sub = s.subSequence(2, 20);

            System.out.println("" + sub);

        } catch (IndexOutOfBoundsException e) {

            System.out.println("Error: " + e); 

        }

    }

}

Error: java.lang.StringIndexOutOfBoundsException: begin 2, end 20, length 11

Explanation:

• The above example shows, how the subSequence() method throws an exception if the end index exceeds the string length.
• It catches and displays the IndexOutOfBoundsException.