java.lang.Integer

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Introduction

The java.lang.Integer class wraps a value of the primitive type int in an object. An object of type Integer contains a single field whose type is int.

Class Declaration

Following is the declaration for java.lang.Integer class −

public final class Integer
  extends Number
    implements Comparable<Integer>

Field

Following are the fields for java.lang.Integer class −

• static int MAX_VALUE − This is a constant holding the maximum value an int can have, 2³¹-1.
• static int MIN_VALUE − This is a constant holding the minimum value an int can have, -2³¹.
• static int SIZE − This is the number of bits used to represent an int value in two's complement binary form.
• static Class<Integer> TYPE − This is the class instance representing the primitive type int.

Class constructors

S.N.	Constructor & Description
1	Integer(int value) This constructs a newly allocated Integer object that represents the specified int value.
2	Integer(String s) This constructs a newly allocated Integer object that represents the int value indicated by the String parameter.

Class methods

S.N.	Method & Description
1	static int bitCount(int i) This method returns the number of one-bits in the two's complement binary representation of the specified int value.
2	byte byteValue() This method returns the value of this Integer as a byte.
3	int compareTo(Integer anotherInteger) This method compares two Integer objects numerically.
4	static Integer decode(String nm) This method decodes a String into an Integer.
5	double doubleValue() This method returns the value of this Integer as a double.
6	boolean equals(Object obj) This method compares this object to the specified object.
7	float floatValue() This method returns the value of this Integer as a float.
8	static Integer getInteger(String nm) This method determines the integer value of the system property with the specified name.
9	static Integer getInteger(String nm, int val) This method determines the integer value of the system property with the specified name.
10	static Integer getInteger(String nm, Integer val) This method returns the integer value of the system property with the specified name.
11	int hashCode() This method returns a hash code for this Integer.
12	static int highestOneBit(int i) This method returns an int value with at most a single one-bit, in the position of the highest-order ("leftmost") one-bit in the specified int value.
13	int intValue() This method returns the value of this Integer as an int.
14	long longValue() This method returns the value of this Integer as a long.
15	static int lowestOneBit(int i) This method returns an int value with at most a single one-bit, in the position of the lowest-order ("rightmost") one-bit in the specified int value.
16	static int numberOfLeadingZeros(int i) This method returns the number of zero bits preceding the highest-order ("leftmost") one-bit in the two's complement binary representation of the specified int value.
17	static int numberOfTrailingZeros(int i) This method returns the number of zero bits following the lowest-order ("rightmost") one-bit in the two's complement binary representation of the specified int value.
18	static int parseInt(String s) This method parses the string argument as a signed decimal integer.
19	static int parseInt(String s, int radix) This method parses the string argument as a signed integer in the radix specified by the second argument.
20	static int reverse(int i) This method returns the value obtained by reversing the order of the bits in the two's complement binary representation of the specified int value.
21	static int reverseBytes(int i) This method returns the value obtained by reversing the order of the bytes in the two's complement representation of the specified int value.
22	static int rotateLeft(int i, int distance) This method returns the value obtained by rotating the two's complement binary representation of the specified int value left by the specified number of bits.
23	static int rotateRight(int i, int distance) This method returns the value obtained by rotating the two's complement binary representation of the specified int value right by the specified number of bits.
24	short shortValue() This method returns the value of this Integer as a short.
25	static int signum(int i) This method returns the signum function of the specified int value.
26	static String toBinaryString(int i) This method returns a string representation of the integer argument as an unsigned integer in base 2.
27	static String toHexString(int i) This method returns a string representation of the integer argument as an unsigned integer in base 16.
28	static String toOctalString(int i) This method returns a string representation of the integer argument as an unsigned integer in base 8.
29	String toString() This method returns a String object representing this Integer's value.
30	static String toString(int i) This method returns a String object representing the specified integer.
31	static String toString(int i, int radix) This method returns a string representation of the first argument in the radix specified by the second argument.
32	static Integer valueOf(int i) This method returns a Integer instance representing the specified int value.
33	static Integer valueOf(String s) This method returns an Integer object holding the value of the specified String.
34	static Integer valueOf(String s, int radix) This method returns an Integer object holding the value extracted from the specified String when parsed with the radix given by the second argument.

Methods inherited

This class inherits methods from the following classes −

• java.lang.Object

//count set(1) bits in a integer

//count set(1) bits in a integer 
public static int coutSetBits(int num)
 {
       int count=0;
       while(num!=0)
               {
                   count+=num&1;
                   num=num>>1;
                }
        return count;
 }

  public static int coutSetBitsUsingBK_Algo(int num)
  {
  int count=0;
      while(num!=0)
  {
  num=num&(num-1);
  count++;
  }
return count;
  }

instanceof Operator

instanceof Operator :

Here's an example of instance of operator.

class instanceofOperator {
    public static void main(String[] args) {
     
     String test = "asdf";
     boolean result;
     
     result = test instanceof String;
     System.out.println(result);
    }
}

Unary Operators

Unary operator performs operation on only one operand.

Operator	Meaning
+	Unary plus (not necessary to use since numbers are positive without using it)
-	Unary minus; inverts the sign of an expression
++	Increment operator; increments value by 1
--	decrement operator; decrements value by 1
!	Logical complement operator; inverts the value of a boolean

Doubly Linked List JAVA

import java.util.Scanner;
public class ImpLinkedList_D
{
  public static void main(String args[])
  {
Scanner scan = new Scanner(System.in);
    DLL objDLL=new DLL();
   int val=0;
 
   do
{
System.out.println("Enter Element: Zero(0) is not allowed");
val=scan.nextInt();
Node_d n=new Node_d();
n.val=val;
n.ref_n=null;
//n.ref_p=null;

if(objDLL.start==null)
{
objDLL.start=n;
objDLL.end=objDLL.start;
}
else
{ 
     
       if(objDLL.end==objDLL.start)
   {
n.ref_p=objDLL.start;
//objDLL.end.ref_p=null;
objDLL.end.ref_n=n;
objDLL.end=n;
   }
   else
   {
n.ref_p=objDLL.end;
objDLL.end.ref_n=n;
//objDLL.end.ref_p=objDLL.end;
objDLL.end=n;
   }
}


System.out.println("CURRENT LIST \n");
printList(objDLL);
}while(val!=0);
 
  }
 
  public static void  printList(DLL objDLL)
  {
   Node_d itrVar=objDLL.start;
   int i=0;
   while(itrVar!=null)
   {
System.out.println("List Element:-"+i+"\n itrVar.val="+itrVar.val+"\n itrVar.ref_p="+itrVar.ref_p+"\n itrVar.Ref_n="+itrVar.ref_n+"\n");
i++;
         itrVar=itrVar.ref_n;
   }
  }

 
}
class DLL
{
  Node_d start;
  Node_d end;
}
class Node_d
{
   int val=0;
   Node_d ref_n;
   Node_d ref_p;
 
}

Single Linked List JAVA

import java.util.Scanner;
public class ImpLinkedList
{
  public static void main(String args[])
  {
Scanner scan = new Scanner(System.in);
    SLL objSLL=new SLL();
   int val=0;
 
   do
{
System.out.println("Enter Element: Zero(0) is not allowed");
val=scan.nextInt();
Node n=new Node();
n.val=val;
n.ref=null;

if(objSLL.start==null)
{
objSLL.start=n;
objSLL.end=objSLL.start;
}
else
{
objSLL.end.ref=n;
objSLL.end=n;
}


System.out.println("CURRENT LIST \n");
printList(objSLL);
}while(val!=0);
 
  }
 
  public static void  printList(SLL objSLL)
  {
   Node itrVar=objSLL.start;
   int i=0;
   while(itrVar!=null)
   {
System.out.println("List Element:-"+i+"\n itrVar.val="+itrVar.val+"\n itrVar.Ref="+itrVar.ref+"\n");
i++;
         itrVar=itrVar.ref;
   }
  }

 
}
class SLL
{
  Node start;
  Node end;
}
class Node
{
   int val=0;
   Node ref;
}

Study Points