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Returns the index within this String of the first occurrence of the specified substring. This method has 4 different variants.

• public int indexOf(int ch) − Returns the index within this string of the first occurrence of the specified character or -1 if the character does not occur.

Syntax

public int indexOf(int ch)

Parameters

ch – The character to search for in the string.

Return Value

Returns the index within this string of the first occurrence of the specified character or -1 if the character does not occur.

• public int indexOf(int ch, int fromIndex) − Returns the index within this string of the first occurrence of the specified character, starting the search at the specified index or 1 if the character does not occur.

Syntax

public int indexOf(int ch, int fromIndex)

Parameters

• ch − The character to search for in the string
• fromIndex − where to start the search from

Return Value

Returns the index within this string of the first occurrence of the specified character, starting the search at the specified index or -1 if the character does not occur.

• int indexOf(String str) − Returns the index within this string of the first occurrence of the specified substring. If it does not occur as a substring, -1 is returned.

Syntax

int indexOf(String str)

Parameters

Str – The string to search for

Return Value

Returns the index within this string of the first occurrence of the specified substring. If it does not occur as a substring, -1 is returned.

• int indexOf(String str, int fromIndex) − Returns the index within this string of the first occurrence of the specified substring, starting at the specified index. If it does not occur, -1 is returned.

Syntax

int indexOf(String str, int fromIndex)

Parameters

str – The string to search for

• fromIndex – where to start the search from

Return Value − Returns the index within this string of the first occurrence of the specified substring, starting at the specified index. If it does not occur, -1 is returned.

Following is an example of the usage of all 4 method variants

class Example { 
   static void main(String[] args) { 
      String a = "Hello World"; 
		
      // Using public int indexOf(int ch) 
      println(a.indexOf('e')); 
      println(a.indexOf('o')); 
		
      // Using public int indexOf(int ch, int fromIndex) 
      println(a.indexOf('l',1)); 
      println(a.indexOf('e',4));
		
      // Using public int indexOf(string str) 
      println(a.indexOf('el')); 
      println(a.indexOf('or')); 
		
      // Using public int indexOf(string str,int fromIndex) 
      println(a.indexOf('el',1)); 
      println(a.indexOf('or',8)); 
   } 
}

When we run the above program, we will get the following result −

1 
4 
2 
-1 
1 
7 
1 
-1

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