Java – String indexOf() Method Example

The method indexOf() is used for finding out the index of the specified character or substring in a particular String. There are 4 variations of this method:
int indexOf(int ch): It returns the index of the first occurrence of character ch in a String.
int indexOf(int ch, int fromIndex): It returns the index of first occurrence if character ch, starting from the specified index “fromIndex”.
int indexOf(String str): Returns the index of string str in a particular String.
int indexOf(String str, int fromIndex): Returns the index of string str, starting from the specified index “fromIndex”.

All the above variations returns -1 if the specified char/substring is not found in the particular String.

Example

public class IndexOfExample{
   public static void main(String args[]) {
       String str1 = new String("This is a BeginnersBook tutorial");
       String str2 = new String("Beginners");
       String str3 = new String("Book");
       String str4 = new String("Books");
       System.out.println("Index of B in str1: "+str1.indexOf('B'));
       System.out.println("Index of B in str1 after 15th char:"+str1.indexOf('B', 15));
       System.out.println("Index of B in str1 after 30th char:"+str1.indexOf('B', 30));
       System.out.println("Index of string str2 in str1:"+str1.indexOf(str2));
       System.out.println("Index of str2 after 15th char"+str1.indexOf(str2, 15));
       System.out.println("Index of string str3:"+str1.indexOf(str3));
       System.out.println("Index of string str4"+str1.indexOf(str4));
       System.out.println("Index of harcoded string:"+str1.indexOf("is"));
       System.out.println("Index of hardcoded string after 4th char:"+str1.indexOf("is", 4));
   }
}

Output:

Index of B in str1: 10
Index of B in str1 after 15th char:19
Index of B in str1 after 30th char:-1
Index of string str2 in str1:10
Index of str2 after 15th char-1
Index of string str3:19
Index of string str4-1
Index of harcoded string:2
Index of hardcoded string after 4th char:5