Java Tutorial/Data Type/Integer

Bit manipulation methods in Integer: bitCount

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));
  }
}

Value in binary: 10101010
Number of one bits: 4

Compare integers using if statements, relational operators and equality operators

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 );
   } 
}

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

Compare Two Java int Arrays

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));
  }
}

Convert a byte array to a Hex string

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
*/

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

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

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

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

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

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

Convert a String to int

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();
    }
  }
}

Convert binary number to decimal number

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

Convert decimal integer to hexadecimal number

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

Convert decimal integer to octal number

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

Convert Decimal to Binary

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 + ".");
  }
}

Convert Decimal to Hexadecimal

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

Convert Decimal to Octal

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);
  }
}

Convert from Byte array to hexadecimal string

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

Convert from decimal to binary

public class Main {
  public static void main(String[] args) throws Exception {
    int i = 42;
    String bin = Integer.toBinaryString(i);
    System.out.println(bin);
  }
}
//101010

Convert from decimal to hexadecimal

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
*/

Convert from decimal to hexadecimal with leading zeroes and uppercase

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

Convert from integer to String

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);
  }
}

Convert from String to integer

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);
  }
}

Convert hexadecimal number to decimal number

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

Convert octal number to decimal number

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

Convert string to an integer or number

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);
  }
}

Create an Integer object

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);
  }
}

Equals Method

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));
  }
}

true

Equivalence

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);
  }
}

false
true

Highest one bit: 128

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

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

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.");
  }
}

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.

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

2147483647
-2147483648

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

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));
  }
}

167772160
-150994945
0

Integer: rotate Left

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);
    }
  }
}

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

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));
  }
}

1
-1
0

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

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);
  }
}

Parse and format a number to decimal

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);
  }
}

Parse and format a number to octal

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);
  }
}

Pass an integer by reference

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

Read Integers from console and calculate

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 );
   }
}

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

Reverse an Integer

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]);
  }
}

Shifted and scaled random integers

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();
      }
   }
}

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.

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

32

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

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