indexOf() ,length() and trim()

Let us understand IndexOf(), length() and trim()

indexOf() method

This method returns the index of first occurrence of a substring or a character or -1 if the character does not occur.

indexOf() method has 4 different overloaded forms

int indexOf(int ch)

It returns the index of the first occurrence of the specified character within this string

int indexOf(String str)

It returns the index of the first occurrence of the specified substring within this string

int indexOf(int ch, int fromIndex)

It returns the index of the first occurrence of the specified character, starting the search at the specified index within this string.

int indexOf(String str, int fromIndex)

It returns the index of the first occurrence of the specified substring, starting at the specified index within this string.

Example

public class StringIndexOfExample {
    public static void main(String[] args) {
        String str="javainsimpleway";
        System.out.println(str.indexOf('a'));   
        System.out.println(str.indexOf('i', 5));    
        String subString="simple";
        System.out.println(str.indexOf(subString)); 
        System.out.println(str.indexOf(subString,8));   
    }   
}

Output

1
7
6
-1

length() method

This method returns the number of characters in the given string

Example :

String str=”java in simple way”;
System.out.println(str.length());

Output

16

Note :
Space is also a character and hence above output is 16 including space

trim() method

This method returns a string by removing any leading and trailing whitespaces.

Method signature

public String trim()

Example :

public class StringTrimExample1{  
public static void main(String args[]){  
String str="  java    ";  
System.out.println(str.trim()); 
}
}  

Output

java


If the whitespaces are between the string, trim() method will not remove such whitespaces, it will remove whitespace at the beginning and end of string

Example

public class StringTrimExample2{  
public static void main(String args[]){  
String str="  java in simple way    ";  
System.out.println(str.trim()); 
}
}

Output

Java in simple way

Raj

Founder of javainsimpleway.com
I love Java and open source technologies and very much passionate about software development.
I like to share my knowledge with others especially on technology 🙂
I have given all the examples as simple as possible to understand for the beginners.
All the code posted on my blog is developed,compiled and tested in my development environment.
If you find any mistakes or bugs, Please drop an email to kb.knowledge.sharing@gmail.com

Connect with me on Facebook for more updates