Java String class methods

The java.lang.String class provides a lot of methods to work on string. By the help of these methods, we can perform operations on string such as trimming, concatenating, converting, comparing, replacing strings etc.

Java String is a powerful concept because everything is treated as a string if you submit any form in window based, web based or mobile application.

Let's see the important methods of String class.

toUpperCase()

The java string toUpperCase() method converts this string into uppercase letter.

Example

snippet

String s="Sachin";
   System.out.println(s.toUpperCase());//SACHIN
   System.out.println(s);//Sachin(no change in original)

Output

SACHIN sachin Sachin

toLowerCase()

The java string toLowerCase() method converts this string into lowercase letter.

Example

snippet

String s="Sachin";
   System.out.println(s.toLowerCase());//sachin
   System.out.println(s);//Sachin(no change in original)

Output

sachin Sachin

trim()

The string trim() method eliminates white spaces before and after string.

Example

snippet

String s="  Sachin  ";
   System.out.println(s);//  Sachin  
   System.out.println(s.trim());//Sachin

Output

Sachin Sachin

startsWith()

Example

snippet

String s="Sachin";
   System.out.println(s.startsWith("Sa"));//true

Output

true

endsWith()

Example

snippet

String s="Sachin";
   System.out.println(s.endsWith("n"));//true

Output

true

charAt()

The string charAt() method returns a character at specified index.

Example

snippet

String s="Sachin";
   System.out.println(s.charAt(0));//S
   System.out.println(s.charAt(3));//h

Output

S h

length()

The string length() method returns length of the string.

Example

snippet

String s="Sachin";
   System.out.println(s.length());//6

Output

intern()

A pool of strings, initially empty, is maintained privately by the class String.

When the intern method is invoked, if the pool already contains a string equal to this String object as determined by the equals(Object) method, then the string from the pool is returned. Otherwise, this String object is added to the pool and a reference to this String object is returned.

Example

snippet

String s=new String("Sachin");
   String s2=s.intern();
   System.out.println(s2);//Sachin

Output

Sachin

valueOf()

The string valueOf() method coverts given type such as int, long, float, double, boolean, char and char array into string.

Example

snippet

int a=10;
  String s=String.valueOf(a);
  System.out.println(s+10);

Output

1010

replace()

The string replace() method replaces all occurrence of first sequence of character with second sequence of character.

Example

snippet

String s1="Java is a programming language. Java is a platform. Java is an Island.";  
String replaceString=s1.replace("Java","Kava");//replaces all occurrences of "Java" to "Kava"  
System.out.println(replaceString);

Output

Kava is a programming language. Kava is a platform. Kava is an Island.