Integer Wrapper class

• Integer  class is present in java.lang package.
• java.lang.Integer  is used to represent integer primitive value in form of object.

Class Definition

1. public final class Integer
2. extends Number 
3. implements Comparable<Integer>

Integer Class Constructors

1.public Integer(int value):

• It takes int primitive value as an argument.

Java code to convert int primitive to Integer object

1. package com.instanceofjavatutorial;
2.  
3. public class IntegerDemo {
4.  
5. public static void main(String[] args) {
6.  
7. 
   
8. 
   
9.  Integer obj=new Integer (37);
10.  
11.  System.out.println(obj);
12.  
13.  
14. }
15. }

Output:

1. 37

2.public Integer(String s)  throws NumberFormatException:

• It takes String value as an argument. 

Java code to convert String to Integer object

1. package com.instanceofjavatutorial;
2.  
3. public class IntegerDemo {
4.  
5. public static void main(String[] args) {
6.  
7. 
   
8. 
   
9.  Integer obj=new Integer ("123");
10.  
11.  System.out.println(obj);
12.  
13.  
14. }
15. }

Output:

1. 123

Integer Class Methods:

3.public static int parseInt(String s) throws NumberFormatException :

• This method takes String as an argument and converts to the int value
• Static method present in Integer Class used to parse the string to the corresponding int value.in
• We can use this method by class name Integer.parseInt("number").
• If the String contains non numeric value then this method throws NumberFormatException 

 Java Program to parse a string or convert String to Integer value

1. package com.instanceofjavatutorial;
2.  
3. public class IntegerParseIntDemo {
4.  
5. public static void main(String[] args) {
6.  
7. 
   
8.  int x= Integer.parseInt("34");
9.   System.out.println(x);
10.  
11.  int y=  Integer.parseInt("56");
12.    System.out.println(y);
13.  
14.  int z=  Integer.parseInt("98");
15.  System.out.println(z);
16.  
17. }
18. }

Output:

1. 34
2. 56
3. 98

4.public int intValue()

• This method returns the int value from the Integer Object.
• obj.intValue()- returns a int value of Object obj.

Java Program to get int value from a Integer Object.

1. package com.instanceofjavatutorial;
2.  
3. public class IntegerIntValueDemo {
4.  
5. public static void main(String[] args) {
6.  
7. 
   
8.  Integer obj= new Integer(25);
9. 
   
10.  
11.  int y= obj.intValue();
12.  
13.  System.out.println(y);
14.  
15. }
16. }

Output:

1. 25

3.public int compareTo(Integer anotherInteger) 

•  This method is used to compare two Integer Objects and returns int value
•  0- Integer is equal to the argument Integer
• < 0 if this Integer is numerically less than the argument Integer
• > 0 if this Integer is numerically greater than the argument

Java Program to compare two Integer Objects.

1. package com.instanceofjavatutorial;
2.  
3. public class IntegercompareToDemo {
4.  
5. public static void main(String[] args) {
6.  
7. 
   
8.    Integer obj1 = new Integer("34");
9.    Integer obj2 = new Integer("08");
10.  
11.   int val =  obj1.compareTo(obj2);
12.  
13.    if(val > 0) {
14.  
15.    System.out.println("obj1 is greater than obj2");
16.  
17.    }
18.    else if(val < 0) {
19.  
20.    System.out.println("obj1 is less than obj2");
21.  
22.    }
23.    else {
24.  
25.    System.out.println("obj1 is equal to obj2");
26.  
27.    }
28. }
29. }

Output:

1. obj1 is greater than obj2

4.public float floatValue()

• This method used to convert integer value to float value.

Java Program to convert Integer to float

1. package com.instanceofjavatutorial;
2.  
3. public class IntegerfloatValueDemo {
4.  
5. public static void main(String[] args) {
6.  
7. 
   
8.    Integer obj1 = new Integer("34");
9.    Integer obj2 = new Integer("23");
10.    
11.     float f 1= obj1.floatValue();
12.     float f 2= obj2.floatValue();
13.  
14.    System.out.println(f1);
15.    System.out.println(f2); 
16. 
    
17. }
18. }

Output:

1. 34.0
2. 23.0

5.public String toString()

• This method used to convert Integer to string object.

Java Program to convert Integer to String Object.

1. package com.instanceofjavatutorial;
2.  
3. public class IntegerfloatValueDemo {
4.  
5. public static void main(String[] args) {
6.  
7. 
   
8.    Integer obj1 = new Integer("12");
9.    Integer obj2 = new Integer("34");
10.    
11.     String  str1= obj1.toString();
12.     String  f 2= obj2.toString();
13.  
14.    System.out.println(str1);
15.    System.out.println(str2); 
16. 
    
17. }
18. }

Output:

1. 12
2. 34