StringBuffer indexOf() method in Java with Examples

In StringBuffer class, there are two types of indexOf() method depending upon the parameters passed to it.

indexOf(String str)

The indexOf(String str) method of StringBuffer class is used to return the index of the String for first occurrence of passed substring as parameter from the sequence contained by this object. If substring str is not present then -1 is returned in place of index. 

Syntax:

public int indexOf(String str)

Parameters: This method accepts str which is substring type value refers to the String whose index we want to get. 

Return Value: This method returns the index of the first occurrence of the passed substring, or -1 if there is no such substring present.

Below programs illustrate the StringBuffer.indexOf() method: 

Example 1: when passed substring is present in the sequence. 

Java

// Java program to demonstrate
// the indexOf() Method.

class GFG {

    public static void main(String[] args)
    {
        // create a StringBuffer object
        // with a String pass as parameter
        StringBuffer str
            = new StringBuffer("GeeksForGeeks");

        // print string
        System.out.println("String: " + str);

        // get index of string For
        int index = str.indexOf("For");

        // print results
        System.out.println("index of 'For': "
                           + index);
    }
}

Output:

String: GeeksForGeeks
index of 'For': 5

Example 2: when passed substring is not present in the sequence. 

Java

// Java program to demonstrate
// the indexOf() Method.

class GFG {

    public static void main(String[] args)
    {
        // create a StringBuffer object
        // with a String pass as parameter
        StringBuffer str
            = new StringBuffer("Geeks for Geeks contribute");

        // print string
        System.out.println("String: " + str);

        // get index of string article
        int index = str.indexOf("article");

        // print results
        System.out.println("index of 'article': "
                           + index);
    }
}

Output:

String: Geeks for Geeks contribute
index of 'article': -1

indexOf(String str, int fromIndex):

The indexOf(String str, int fromIndex) method of StringBuffer class is used to return the index within the String for first occurrence of passed substring starting from the specified index ‘fromIndex’. If substring str is not present then -1 is returned. fromIndex is Integer type value refers to the index of the start of the search. If string present before the index of the start of search but not after then -1 will return. Syntax:

public int indexOf(String str, int fromIndex)

Parameters: This method accepts two one parameters str which is String type value refers to the String whose index we want to get and fromIndex which is Integer type value refers to the index from which to start the search. 

Returns: This method returns the index of the first occurrence of the passed substring starting at the specified index, or -1 if there is no such substring present. 

Below programs illustrate the StringBuffer.indexOf() method: 

Example 1: when passed substring is present in the sequence. 

Java

// Java program to demonstrate
// the indexOf() Method.

class GFG {

    public static void main(String[] args)
    {
        // create a StringBuffer object
        // with a String pass as parameter
        StringBuffer str
            = new StringBuffer("GeeksForGeeks");

        // print string
        System.out.println("String: " + str);

        // get index of string For from index 3
        int index = str.indexOf("For", 3);

        // print results
        System.out.println("index of 'For': "
                           + index);
    }
}

Output:

String: GeeksForGeeks
index of 'For': 5

Example 2: when passed substring is present in the sequence but index of search is greater than index of substring. 

Java

// Java program to demonstrate
// the indexOf() Method.

class GFG {

    public static void main(String[] args)
    {
        // create a StringBuffer object
        // with a String pass as parameter
        StringBuffer str
            = new StringBuffer("Geeks for Geeks contribute");

        // print string
        System.out.println("String: " + str);

        // get index of string Geeks from index 15
        int index = str.indexOf("Geeks", 15);

        // print results
        System.out.println("index of 'Geeks ': "
                           + index);
    }
}

Output:

String: Geeks for Geeks contribute
index of 'Geeks ': -1

References: https://docs.oracle.com/javase/10/docs/api/java/lang/StringBuffer.html#indexOf(java.lang.String, int) https://docs.oracle.com/javase/10/docs/api/java/lang/StringBuffer.html#indexOf(java.lang.String)