String Class in Java

String Class in Java

It is a predefined class in java.lang package can be used to handle the String. String class is immutable that means whose content can not be changed at the time of execution of program.

String class object is immutable that means when we create an object of String class it never changes in the existing object.
Example:

class StringHandling
{
public static void main(String arg[])
{
String s=new String("java"); 
s.concat("software");
System.out.println(s);
}
}

java

Explanation: Here we can not change the object of String class so output is only java not java software.

Methods of String class

length()

length(): This method is used to get the number of character of any string.

class StringHandling
{
public static void main(String arg[])
{
int l;
String s=new String("Java"); 
l=s.length();
System.out.println("Length: "+l);
}
}

Length: 4

charAt(index)

charAt(): This method is used to get the character at a given index value.

class StringHandling
{
public static void main(String arg[])
{
char c;
String s=new String("Java"); 
c=s.charAt(2);
System.out.println("Character: "+c);
}
}

Character: v

toUpperCase()

toUpperCase(): This method is use to convert lower case string into upper case.

class StringHandling
{
public static void main(String arg[])
{
String s="Java"; 
System.out.println("String: "+s.toUpperCase());
}
}

String: JAVA

toLowerCase()

toLowerCase(): This method is used to convert lower case string into upper case.

class StringHandling
{
public static void main(String arg[])
{
String s="JAVA"; 
System.out.println("String: "+s.toLowerCase());
}
}

String: java

concat()

concat(): This method is used to combined two string.

class StringHandling
{
public static void main(String arg[])
{
String s1="Hitesh";
String s2="Raddy"; 
System.out.println("Combined String: "+s1.concat(s2));
}
}

Combined String: HiteshRaddy

equals()

equals(): This method is used to compare two strings, It return true if strings are same otherwise return false. It is case sensitive method.

class StringHandling
{
public static void main(String arg[])
{
String s1="Hitesh";
String s2="Raddy"; 
String s3="Hitesh";
System.out.println("Compare String: "+s1.equals(s2));
System.out.println("Compare String: "+s1.equals(s3));
}
}

Compare String: false
Compare String: true

equalsIgnoreCase()

equalsIgnoreCase(): This method is case insensitive method, It return true if the contents of both strings are same otherwise false.

class StringHandling
{
public static void main(String arg[])
{
String s1="Hitesh";
String s2="HITESH"; 
String s3="Raddy";
System.out.println("Compare String: "+s1.equalsIgnoreCase(s2));
System.out.println("Compare String: "+s1.equalsIgnoreCase(s3));
}
}

Compare String: true
Compare String: false

compareTo()

compareTo(): This method is used to compare two strings by taking unicode values, It return 0 if the string are same otherwise return +ve or -ve integer values.

class StringHandling
{
public static void main(String arg[])
{
String s1="Hitesh";
String s2="Raddy";
int i;
i=s1.compareTo(s2);
if(i==0)
{
System.out.println("Strings are same");
}
else
{
System.out.println("Strings are not same");
}
}
}

Strings are not same

compareToIgnoreCase()

compareToIgnoreCase(): This method is case insensitive method, which is used to compare two strings similar to compareTo().

class StringHandling
{
public static void main(String arg[])
{
String s1="Hitesh";
String s2="HITESH";
int i;
i=s1.compareToIgnoreCase(s2);
if(i==0)
{
System.out.println("Strings are same");
}
else
{
System.out.println("Strings are not same");
}
}
}

Strings are same

startsWith()

startsWith(): This method return true if string is start with given another string, otherwise it returns false.

class StringHandling
{
public static void main(String arg[])
{
String s="Java is programming language";
System.out.println(s.startsWith("Java"));
}
}

true

endsWith()

endsWith(): This method return true if string is end with given another string, otherwise it returns false.

class StringHandling
{
public static void main(String arg[])
{
String s="Java is programming language";
System.out.println(s.endsWith("language"));
}
}

true

subString()

subString(): This method is used to get the part of given string.

class StringHandling
{
public static void main(String arg[])
{
String s="Java is programming language";
System.out.println(s.substring(8)); // 8 is starting index
}
}

programming language

class StringHandling
{
public static void main(String arg[])
{
String s="Java is programming language";
System.out.println(s.substring(8, 12));
}
}

prog

indexOf()

indexOf(): This method is used find the index value of given string. It always gives starting index value of first occurrence of string.

class StringHandling
{
public static void main(String arg[])
{
String s="Java is programming language";
System.out.println(s.indexOf("programming"));
}
}

8

lastIndexOf()

lastIndexOf(): This method used to return the starting index value of last occurence of the given string.

class StringHandling
{
public static void main(String arg[])
{
String s1="Java is programming language";
String s2="Java is good programming language";
System.out.println(s1.lastIndexOf("programming"));
System.out.println(s2.lastIndexOf("programming"));
}
}

8
13

trim()

trim(): This method remove space which are available before starting of string and after ending of string.

class StringHandling
{
public static void main(String arg[])
{
String s="    Java is programming language    ";
System.out.println(s.trim());
}
}

Java is programming language

split()

split(): This method is used to divide the given string into number of parts based on delimiter (special symbols like @ space , ).

class StringHandling
{
public static void main(String arg[])
{
String s="contact@tutorial4us.com";
String[] s1=s.split("@");  // divide string based on @
for(String c:s1) //  foreach loop 
{
System.out.println(c); 
}
}
}

contact
@tutorial4us.com

replace()

replace(): This method is used to return a duplicate string by replacing old character with new character.

Note: In this method data of original string will never be modify.

class StringHandling
{
public static void main(String arg[])
{
String s1="java";
String s2=s1.replace('j', 'k');
System.out.println(s2);
}
}

kava