Java String indexOf() method

Java String indexOf() method returns index of a given character or substring present in a String.

Methods Description

int indexOf(int ch)	It returns index position for the given char value.
int indexOf(int ch, int fromIndex)	It returns index position for the given char value and from index.
int indexOf(String substring)	It returns index position for the given substring.
int indexOf(String substring, int fromIndex)	It returns index position for the given substring and from index.

Parameters:

ch: a single character

fromIndex: index position from where index of the char value or substring is returned

substring: substring to be searched in this string

Return:

It returns index of the character within a String

Java String IndexOf() method Example 1

public class JavaStringIndexOfEx1{ 
public static void main(String args[]){ 
String s1="welcome to tutorial and example"; 
//passing substring 
int index1=s1.indexOf("to"); 
int index2=s1.indexOf("and"); 
System.out.println(index1+"  "+index2);
//passing substring with from index 
int index3=s1.indexOf("to",9);
int index4=s1.indexOf("to",5);
System.out.println(index3);
System.out.println(index4);
//passing char value 
int index5=s1.indexOf('a'); 
int index6=s1.indexOf('z'); 
System.out.println(index5); 
System.out.println(index6); 
  }
}

Output:

 8   20 13 8 17 -1

Java String indexOf(String substring) Method Example 2

public class JavaStringIndexOfEx2 { 
    public static void main(String[] args) { 
        String s1 = "India is a great ";
        String s2 = s1.concat("Country in the world");
        // Passing Substring   
        int index = s2.indexOf("the"); //Returns the index of this substring 
         int index2 = s1.indexOf("the");
         int index3 = s2.indexOf("a");
         int index4 = s2.indexOf(" ");
        System.out.println("index of substring "+index);
        System.out.println("index of substring "+index2);
        System.out.println("index of substring "+index3);
        System.out.println("index of substring "+index4);
    } 
}

Output:

index of substring 28
index of substring -1
index of substring 4
index of substring 5

Java String indexOf(String substring, int fromIndex) Method Example 3

public class JavaStringIndexOfEx3 { 
    public static void main(String[] args) { 
        String s1 = "India is a great ";
        String s2 = s1.concat("Country in the world");
        // Passing substring and index    
        int index = s2.indexOf("the", 10); //Returns the index of this substring 
         int index2 = s1.indexOf("the", 5);
         int index3 = s2.indexOf("a", 25);
         //Passing substring
         int index4 = s2.indexOf(" ");
        System.out.println("index of substring "+index);//Returns the index of this substring 
        System.out.println("index of substring "+index2);
        System.out.println("index of substring "+index3);// It returns -1 if substring does not found 
        System.out.println("index of substring "+index4);
    } 
  }

Output:

index of substring 28
index of substring -1
index of substring -1
index of substring 5