Java.lang.String.indexOf() Method

Description

The java.lang.String.indexOf(String str) method returns the index within this string of the first occurrence of the specified substring. The integer returned is the smallest value k such that: this.startsWith(str, k) is true.

Declaration

Following is the declaration for java.lang.String.indexOf() method

public int indexOf(String str)

Parameters

str − This is value of a string.

Return Value

This method returns if the string argument occurs as a substring within this object, then the index of the first character of the first such substring is returned; if it does not occur as a substring, -1 is returned.

Exception

NA

Example

The following example shows the usage of java.lang.String.indexOf() method.

package com.tutorialspoint;

import java.lang.*;

public class StringDemo {

   public static void main(String[] args) {

      String str1 = "Collections of tutorials at tutorials point";
     
      // returns index of first character of the substring "tutorials" 
      System.out.println("index =  " + str1.indexOf("tutorials")); 
      
      // returns -1 as substring "admin" is not located
      System.out.println("index =  " + str1.indexOf("admin"));    
   }
}

Let us compile and run the above program, this will produce the following result −

index = 15
index = -1