What is String in Java

→ String is a sequence of characters, in double quotation mark.

→ String an object in java.

→ String is an array of characters .

Example

char[] ch={'h','e','l','l','o'};  
String s=new String(ch);

How to create string object:

→ There are 2 ways to create String object

String Literal
new keyword

1) String Literal

→ String Literal contain "double quotes" String Value.

Example

 public  class Bhr{    
    public static void main(String[] args) {  
    	String s1 = "ElibraryPortal";
    	System.out.println(s1);
    }  
}   

Output:

2) new keyword

→ When we can create String object using new keyword for that allocates memory for the object. . String class has many constructors to create String objects using different sources, such as string literal, an array of characters etc.

Example

public class StringEx {  
public static void main(String args[]){  
String s1="java";//creating string by java string literal  
char ch[]={'s','t','r','i','n','g','s'};  
String s2=new String(ch);//converting char array to string  
String s3=new String("example");//creating java string by new keyword  
System.out.println(s1);  
System.out.println(s2);  
System.out.println(s3);  
}}  

Output

java
strings
example

String Method in Java

There are some use full Method are used in this chapter that is.

String length()
String compareTo()
String concat()
String IsEmpty()
String Trim()
String toLowerCase()
String toUpper()
String ValueOf()

1) Java String length() :-

→ length() Method returns count of total number of characters present in the String.

Example:

public class StringLenthEx{
public static void main(String args[]){ 
String s1="Elibraryportal"; 
String s2="E Library Portal"; 
System.out.println("String Length is: "+s1.length());  
System.out.println("String Length count with space : "+s2.length()); 
}}

Output:

2) Java String compareTo() :-

→ compareTo() method compares the given string with current string. It either returns positive number or negative number or 0.

Example:

public class CompareToExample{ 
public static void main(String args[]){ 
String s1="hello";
String s2="hello"; 
String s3="hemlo"; 
String s4="flag";
System.out.println(s1.compareTo(s2)); // 0 because both are equal
System.out.println(s1.compareTo(s3)); //-1 because "l" is only one time lower than "m" 
System.out.println(s1.compareTo(s4)); // 2 because "h" is 2 times greater than "f"
}} 

Output:

3) Java String concat() :-

→ concat() method is used to add two or more string into a single string object.or You can say append of another string.

Example:

public class ConcatExample{
public static void main(String args[]){
String s1="E Library";
s1=s1.concat("Portal");
System.out.println(s1);
}}

Output:

4) Java String IsEmpty() :-

→ IsEmpty() method checks string is empty or not. If the java String is Empty, it returns true otherwise else returns false.

Example:

public class IsEmptyEx { 
public static void main(String args[]){ 
String s1=""; 
String s2="hello"; 
System.out.println(s1.isEmpty());      // true
System.out.println(s2.isEmpty());      // false
}}

Output:

5) Java String Trim() :-

→ Trim() Method Remove whitespace from both sides of a string:

Example:

 public class StringTrimEx{  
 public static void main(String args[]){  
String s1="    Hello     ";  
System.out.println(s1+"how are you");        // without trim()  
System.out.println(s1.trim()+"how are you"); // with trim()  
}} 

Output:

6) Java String toLowerCase() :-

→ toLowerCase() method converts all the characters of the String in lower case letter.

Example:

public class ToLowerExample {
  public static void main(String[] args) {
    String txt = "Hello World";     
    System.out.println(txt.toLowerCase());
  }}

Output:

7) Java String toUpper() :-

→ toUpper() converts all the characters of the String in Upper case letter.

Example:

public class ToUpperex {
  public static void main(String[] args) {
    String txt = "Hello World";
    System.out.println(txt.toUpperCase());    
  }}

Output:

8) Java String ValueOf() :-

→ ValueOf() Method converts different types of values into string such as long to string, boolean to string, character to string, float to string, double to string, object to string and char array to string etc.

String valueOf() method in Java

valueOf(boolean b) :- Returns the boolean argument.
valueOf(char c) :- Returns the char argument
valueOf(char[] data) :- Returns the char array argument.
valueOf(char[] data, int offset, int count) :- Returns the string a specific sub array of the char array argument.
valueOf(double d) :- Returns the of the double argument.
valueOf(float f) :- Returns the float argument.
valueOf(int i) :- Returns the int argument.
valueOf(long l) :- Returns the long argument.
valueOf(Object obj) :- Returns the Object argument.

Example:

 import java.io.*;
public class ValueOfExample {
   public static void main(String args[]) {
      double d = 102939939.939;
      boolean b = true;
      long l = 1232874;
      char[] arr = {'a', 'b', 'c', 'd', 'e', 'f','g' };

      System.out.println("Return Value : " + String.valueOf(d) );
      System.out.println("Return Value : " + String.valueOf(b) );
      System.out.println("Return Value : " + String.valueOf(l) );
      System.out.println("Return Value : " + String.valueOf(arr) );
   }}

Output:

Next TopicImmutable or (Unchangeable) String in Java

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String Java

What is String in Java

Example

How to create string object:

1) String Literal

Example

2) new keyword

Example

String Method in Java

1) Java String length() :-

2) Java String compareTo() :-

3) Java String concat() :-

4) Java String IsEmpty() :-

5) Java String Trim() :-

6) Java String toLowerCase() :-

7) Java String toUpper() :-

8) Java String ValueOf() :-

String valueOf() method in Java