Advertisement

---

Top

< Prev

Next >

The indexOf() method of String class determines the index of the first occurrence of a particular String or a character within a String object.

Some versions of indexOf() method




Methods	Description
public int indexOf(char ch)	It returns the first index of the char ch found in the String object.
public int indexOf(String str)	It returns the first index of the String str found in the String object.








Method index() to search a char index in a String object.


We are searching for the index of a particular char value in a String object using indexOf() method. If the searched char is found, its first index is returned, otherwise if the charis not found then -1 is returned.

// Program to find a particular character in a String.

class StringIndex1
{
public static void main(String[] ar)
{
String str1= new String("Java Rules, Java");

int index1 = str1.indexOf('v');
int index2 = str1.indexOf('a');
int index3 = str1.indexOf('z');

System.out.println("First Index of 'v' in " + str1 +  " : "+ index1);
System.out.println("First Index of 'a' in " + str1 +  " : "+ index2);
System.out.println("First Index of 'z' in " + str1 +  " : "+ index3);
}
}





Output is :




Index of 'v' in Java Rules, Java : 2
Index of 'a' in Java Rules, Java : 1
Last Index of 'z' in Java Rules, Java : -1





Program Analysis



String is initialized with value Java Rules, Java
• Index of the first occurrence of char value v in the String object is found 2.
• Index of the first occurrence of char value a in the String object is found 1.
• Index of the first occurrence of char value z in the String object is not found, hence -1 is returned.







Method index() to search a String index in a String object.


Here in this next example, we are searching for the index of a particular String value in a String object using indexOf() method. If the searched String is found, its first index is returned, otherwise if the String is not found then -1 is returned.

// Program to find a particular character in a String.

class StringIndex1
{
public static void main(String[] ar)
{
String str1= new String("Blue Sky Blue");

int index1 = str1.indexOf("Blue");
int index2 = str1.indexOf("Sky");
int index3 = str1.indexOf("Hi");

System.out.println("First Index of Blue in " + str1 +  " : "+ index1);
System.out.println("First Index of Sky  in " + str1 +  " : "+ index2);
System.out.println("First Index of Hi   in " + str1 +  " : "+ index3);
}
}





Output is :




First Index of Blue in Blue Sky Blue : 0
First Index of Sky  in Blue Sky Blue : 5
First Index of Hi  in Blue Sky Blue : -1





Program Analysis



String is initialized with value Blue Sky Blue
• Index of the first occurrence of String value Blue in the String object is found 0.
• Index of the first occurrence of String value Sky in the String object is found 5.
• Index of the first occurrence of String value Hi in the String object is not found, hence -1 is returned.





Advertisement






Method indexOf() performs a case-sensitive search.


Both forms of indexOf() method perform a case-sensitive search, whether it comes to the search of an index of a char or String value in a String object.

// Program to find a particular character in a String.

class StringIndex1
{
public static void main(String[] ar)
{
String str1= new String("Jazz joy"); 
String str2= new String("Live and let live");

int index1 = str1.indexOf('j');
int index2 = str2.indexOf("live");

System.out.println("First Index of j in " + str1 +  " : "+ index1);
System.out.println("First Index of live in " + str2 +  " : "+ index2);
}
}





Output is :




Last Index of j in Jazz joy : 5
Last Index of live in live and let live : 13





Program Analysis



First String is initialized with value Jazz joy, second String is initialized with value Live and let live.
• Index of the first occurrence of char value lower case Z in the first String object is found 5.
• Index of the first occurrence of String value live in the second String object is found 13.






Please share this article -






< Prev
Next >
< lastIndexOf() method
split() method >



Advertisement