Java Tutorial/Data Type/Integer

Bit manipulation methods in Integer: bitCount

   <source lang="java">

public class MainClass {

 public static void main(String args[]) {
   int n = 170; // 10101010
   System.out.println("Value in binary: 10101010");
   System.out.println("Number of one bits: " + Integer.bitCount(n));
 }

}</source>

Value in binary: 10101010
Number of one bits: 4

Compare integers using if statements, relational operators and equality operators

   <source lang="java">

import java.util.Scanner; public class MainClass {

  public static void main( String args[] )
  {
     Scanner input = new Scanner( System.in );
     int number1;
     int number2;
     System.out.print( "Enter first integer: " ); // prompt 
     number1 = input.nextInt(); // read first number from user 
     System.out.print( "Enter second integer: " ); // prompt 
     number2 = input.nextInt(); // read second number from user 
     
     if ( number1 == number2 ) 
        System.out.printf( "%d == %d\n", number1, number2 );
     if ( number1 != number2 )
        System.out.printf( "%d != %d\n", number1, number2 );
     if ( number1 < number2 )
        System.out.printf( "%d < %d\n", number1, number2 );
     if ( number1 > number2 )
        System.out.printf( "%d > %d\n", number1, number2 );
     if ( number1 <= number2 )
        System.out.printf( "%d <= %d\n", number1, number2 );
     if ( number1 >= number2 )
        System.out.printf( "%d >= %d\n", number1, number2 );
  } 

}</source>

Enter first integer: 2
Enter second integer: 3
2 != 3
2 < 3
2 <= 3

Compare Two Java int Arrays

   <source lang="java">

import java.util.Arrays; public class Main {

 public static void main(String[] args) {
   int[] a1 = new int[] { 2, 7, 1 };
   int[] a2 = new int[] { 2, 7, 1 };
   System.out.println(Arrays.equals(a1, a2));
 }

}</source>

Convert a byte array to a Hex string

   <source lang="java">

public class Main {

 public static void main(String[] argv) {
   byte[] b = "ada".getBytes();
  
   for (int i = 0; i < b.length; i++) {
     System.out.println(Integer.toString((b[i] & 0xff) + 0x100, 16).substring(1));
   }
   
 }

} /* 61 64 61

• /</source>

Convert an int value to String: concatenate string to an int value

   <source lang="java">

public class Main {

 public static void main(String[] args) {
   int i = 50;
   String str = "" + i;
   System.out.println(str + " : " + ("" + i).getClass());
 }

} // 50 : class java.lang.String</source>

Convert an int value to String: Integer.toString(i)

   <source lang="java">

public class Main {

 public static void main(String[] args) {
   int i = 50;
   String str = Integer.toString(i);
   System.out.println(str + " : " + Integer.toString(i).getClass());
 }

} //50 : class java.lang.String</source>

Convert an int value to String: new Integer(i).toString()

   <source lang="java">

public class Main {

 public static void main(String[] args) {
   int i = 50;
   String str = new Integer(i).toString();
   System.out.println(str + " : " + new Integer(i).toString().getClass());
 }

} //50 : class java.lang.String</source>

Convert a String to int

   <source lang="java">

public class Main {

 public static void main(String[] argv) {
   String sValue = "5";
   try {
     int iValue = Integer.parseInt(sValue);
     System.out.println(iValue);
   } catch (NumberFormatException ex) {
     ex.printStackTrace();
   }
 }

}</source>

Convert binary number to decimal number

   <source lang="java">

public class Main {

 public static void main(String[] args) {
   System.out.println(Integer.parseInt("111000", 2));
 }

}</source>

Convert decimal integer to hexadecimal number

   <source lang="java">

public class Main {

 public static void main(String[] args) {
   System.out.println(Integer.toHexString(32));
 }

}</source>

Convert decimal integer to octal number

   <source lang="java">

public class Main {

 public static void main(String[] args) {
   System.out.println(Integer.toOctalString(27));
 }

}</source>

Convert Decimal to Binary

   <source lang="java">

public class Main {

 public static void main(String[] args) {
   int integer = 127;
   String binary = Integer.toBinaryString(integer);
   System.out.println("Binary value of " + integer + " is " + binary + ".");
   int original = Integer.parseInt(binary, 2);
   System.out.println("Integer value of binary "" + binary + "" is " + original + ".");
 }

}</source>

Convert Decimal to Hexadecimal

   <source lang="java">

public class Main {

 public static void main(String[] args) {
   System.out.println(Integer.toHexString(1976));
   System.out.println(Integer.parseInt("7b8", 16));
 }

}</source>

Convert Decimal to Octal

   <source lang="java">

public class Main {

 public static void main(String[] args) {
   int integer = 1024;
   String octal = Integer.toOctalString(integer);
   System.out.printf("Octal value of %d is "%s".\n", integer, octal);
   System.out.printf("Octal value of %1$d is "%1$o".\n", integer);
   int original = Integer.parseInt(octal, 8);
   System.out.printf("Integer value of octal "%s" is %d.", octal, original);
 }

}</source>

Convert from Byte array to hexadecimal string

   <source lang="java">

public class Main {

 public static void main(String[] args) throws Exception {
   int i = Integer.valueOf("1234A", 16).intValue();
   // or
   i = Integer.parseInt("BBA", 16);
 }

}</source>

Convert from decimal to binary

   <source lang="java">

public class Main {

 public static void main(String[] args) throws Exception {
   int i = 42;
   String bin = Integer.toBinaryString(i);
   System.out.println(bin);
 }

} //101010</source>

Convert from decimal to hexadecimal

   <source lang="java">

public class Main {

 public static void main(String[] args) throws Exception {
   int i = 42;
   String hexstr = Integer.toString(i, 16);
   System.out.println(hexstr);
   hexstr = Integer.toHexString(i);
   System.out.println(hexstr);
   
 }

} /* 2a 2a

• /</source>

Convert from decimal to hexadecimal with leading zeroes and uppercase

   <source lang="java">

public class Main {

 public static void main(String[] args) throws Exception {
    System.out.print(Integer.toHexString(0x10000 | i).substring(1).toUpperCase());
 }

}</source>

Convert from integer to String

   <source lang="java">

public class Main {

 public static void main(String[] args) throws Exception {
   int i = 2;
   String str = Integer.toString(i);
   System.out.println(str);
   // or
   str = "" + i;
   System.out.println(str);
 }

}</source>

Convert from String to integer

   <source lang="java">

public class Main {

 public static void main(String[] args) throws Exception {
   String str = "25";
   int i = Integer.valueOf(str).intValue();
   // or
   i = Integer.parseInt(str);
 }

}</source>

Convert hexadecimal number to decimal number

   <source lang="java">

public class Main {

 public static void main(String[] args) {
   System.out.println(Integer.parseInt("20", 16));
 }

}</source>

Convert octal number to decimal number

   <source lang="java">

public class Main {

 public static void main(String[] args) {
   System.out.println(Integer.parseInt("33", 8));
 }

}</source>

Convert string to an integer or number

   <source lang="java">

public class Main {

 public static void main(String[] args) {
   String myNumber = "13";
   Integer number = Integer.parseInt(myNumber);
   System.out.println("My lucky number is: " + number);
   number = Integer.parseInt(myNumber, 16);
   System.out.println("My lucky number is: " + number);
   number = Integer.parseInt(myNumber, 8);
   System.out.println("My lucky number is: " + number);
 }

}</source>

Create an Integer object

   <source lang="java">

public class Main {

 public static void main(String[] args) {
   Integer intObj1 = new Integer(10);
   Integer intObj2 = new Integer("10");
   System.out.println(intObj1);
   System.out.println(intObj2);
 }

}</source>

Equals Method

   <source lang="java">

public class MainClass {

 public static void main(String[] args) {
   Integer n1 = new Integer(47);
   Integer n2 = new Integer(47);
   System.out.println(n1.equals(n2));
 }

}</source>

true

Equivalence

   <source lang="java">

public class MainClass {

 public static void main(String[] args) {
   Integer n1 = new Integer(47);
   Integer n2 = new Integer(47);
   System.out.println(n1 == n2);
   System.out.println(n1 != n2);
 }

}</source>

false
true

Highest one bit: 128

   <source lang="java">

public class MainClass {

 public static void main(String args[]) {
   int n = 170;
   System.out.println("Highest one bit: " + Integer.highestOneBit(n));
 }

}</source>

Integer.lowestOneBit(n), Integer.numberOfLeadingZeros(n), Integer.numberOfTrailingZeros(n)

   <source lang="java">

public class MainClass {

 public static void main(String args[]) {
   int n = 170;
   System.out.println("Lowest one bit: " + Integer.lowestOneBit(n));
   System.out.println("Number of leading zeros : " + Integer.numberOfLeadingZeros(n));
   System.out.println("Number of trailing zeros : " + Integer.numberOfTrailingZeros(n));
   System.out.println("\nBeginning with the value 1, " + "rotate left 16 times.");
 }

}</source>

Lowest one bit: 2
Number of leading zeros : 24
Number of trailing zeros : 1
Beginning with the value 1, rotate left 16 times.

Integer: MAX, MIN VALUE

A constant holding the maximum value an int can have, 2^31-1.

A constant holding the minimum value an int can have, -2^31.

   <source lang="java">

public class MainClass {

 public static void main(String[] arg) {
   System.out.println(Integer.MAX_VALUE);   
   System.out.println(Integer.MIN_VALUE);   
 }

}</source>

2147483647
-2147483648

Integer.reverseBytes( ) reverses the order of the bytes in num and returns the result

   <source lang="java">

public class MainClass {

 public static void main(String args[]) {
     System.out.println(Integer.reverseBytes(10));
     System.out.println(Integer.reverseBytes(-10));
     System.out.println(Integer.reverseBytes(0));
 }

}</source>

167772160
-150994945
0

Integer: rotate Left

   <source lang="java">

public class MainClass {

 public static void main(String args[]) {
   int n = 1;
   for (int i = 0; i < 16; i++) {
     n = Integer.rotateLeft(n, 1);
     System.out.println(n);
   }
 }

}</source>

2
4
8
16
32
64
128
256
512
1024
2048
4096
8192
16384
32768
65536

Integer signum() returns

1. -1 if num is negative
2. 0 if it is zero, and
3. 1 if it is positive

   <source lang="java">

public class MainClass {

 public static void main(String args[]) {
     System.out.println(Integer.signum(10));
     System.out.println(Integer.signum(-10));
     System.out.println(Integer.signum(0));
 }

}</source>

1
-1
0

Java int:int is 32 bit signed type ranges from � to .

   <source lang="java">

public class Main {

 public static void main(String[] args) {
   int i = 0;
   int j = 100;
   System.out.println("Value of int variable i is :" + i);
   System.out.println("Value of int variable j is :" + j);
 }

}</source>

Parse and format a number to decimal

   <source lang="java">

public class Main {

 public static void main(String[] argv) throws Exception {
   int i = Integer.parseInt("1023");
   String s = Integer.toString(i);
   System.out.println(s);
 }

}</source>

Parse and format a number to octal

   <source lang="java">

public class Main {

 public static void main(String[] argv) throws Exception {
   int i = Integer.parseInt("1000", 8);
   String s = Integer.toString(i, 8);
   System.out.println(s);
 }

}</source>

Pass an integer by reference

   <source lang="java">

public class Main {

 public static void main(String[] argv) {
   int[] a = new int[1];
   a[0] = 1;
   add(a);
   System.out.println(a[0]);
 }
 static void add(int[] a) {
   a[0] = a[0] + 2;
 }

} // 3</source>

Read Integers from console and calculate

   <source lang="java">

import java.util.Scanner; public class MainClass {

  public static void main( String args[] )
  {
     Scanner input = new Scanner( System.in );
     int x;
     int y;
     int z;
     int result;
     System.out.print( "Enter first integer: " );
     x = input.nextInt();
     System.out.print( "Enter second integer: " );
     y = input.nextInt();
     
     System.out.print( "Enter third integer: " );
     z = input.nextInt();
     result = x * y * z;
     System.out.printf( "Product is %d\n", result );
  }

}</source>

Enter first integer: 1
Enter second integer: 2
Enter third integer: 3
Product is 6

Reverse an Integer

   <source lang="java">

class ReverseInt {

 public static void main(String[] args) {
   int num = 1234567890;
   int[] digits = { 0, 0, 0, 0, 0, 0, 0, 0, 0, 0 };
   int i = 0;
   while (num != 0) {
     digits[i++] = num % 10;
     num /= 10;
   }
   for (i = 0; i < digits.length; i++)
     System.out.print(digits[i]);
 }

}</source>

Shifted and scaled random integers

   <source lang="java">

import java.util.Random; public class MainClass {

  public static void main( String args[] )
  {      
     Random randomNumbers = new Random(); // random number generator
     int face; // stores each random integer generated
     for ( int i = 1; i <= 20; i++ ) 
     {
        // pick random integer from 1 to 6
        face = 1 + randomNumbers.nextInt( 6 );
        System.out.printf( "%d  ", face );
        
        // if i is divisible by 5, start a new line of output
        if ( i % 5 == 0 )
           System.out.println();
     }
  }

}</source>

3  6  4  1  1  
2  5  6  5  1  
2  6  2  3  2  
1  5  1  2  4

The number of bits used to represent an int value in two"s complement binary form.

   <source lang="java">

public class MainClass {

 public static void main(String[] arg) {
   System.out.println(Integer.SIZE);   
 }

}</source>

32

To catch illegal number conversion, try using the try/catch mechanism.

   <source lang="java">

public class Main {

 public static void main(String[] args) throws Exception {
   try {
     int i = Integer.parseInt("asdf");
   } catch (NumberFormatException e) {
     ;
   }
 }

}</source>