Operator Example Questions

Q. int num1 is 10, num2 is 20, and num3 is 30.  What is the value of the each variables after following code?
num1=num2=num3;

A.

public class Test
{
 public static void main(String[] args)
 {
  int num1=10;
  int num2=20;
  int num3=30;
  
  num1=num2=num3;
  
  System.out.println(num1);
  System.out.println(num2);
  System.out.println(num3);
 }
}

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Q. Here is a code.  'num2+=10' is not working in this code.  Fix it to increase the value of 'num2.'

public class Test
{
 public static void main(String[] args)
 {
  int num1=0, num2=0;
  boolean result;
  
  result = (num1+=10)<0 && (num2+=10)>0;
  System.out.println("result="+result);
  System.out.println("num1="+num1+", num2="+num2);
  
  result = (num1+=10) > 0 || (num2+=10) >0;
  System.out.println("Result = " + result);
  System.out.println("num1 = " + num1 + ", num2 = " + num2);
 }
}

A.

public class Test
{
 public static void main(String[] args)
 {
  int num1=0, num2=0;
  boolean result;
  
  num1+=10;
  num2+=10;
  result = (num1<0) && (num2>0);
  System.out.println("result = " + result);
  System.out.println("num1 = " + num1 + ", num2 = " + num2);
  
  num1+=10;
  num2+=10;
  result = (num1>0) || (num2>0);
  System.out.println("result = " + result);
  System.out.println("num1 = " + num1 + ", num2 = " + num2);
 }
}

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Q. Write a program to calculate: {(25*5)+(36-4)-72}/5

A.

public class Test
{
 public static void main(String[] args)
 {
  int ans = ((25*5)+(3604)-72)/5;
  System.out.println(ans);
 }
}

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Q. Write a program for calculating 3+6, 3+6+9, 3+6+9+14 with minimum times of adding.

A.

public class Test
{
 public static void main(String[] args)
 {
  int result=3+6;
  System.out.println(result);
  
  result +=9;
  System.out.println(result);
  
  result +=12;
  System.out.println(result);
 }
}

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Q. A={(25+5)+(36/4)-72}*5, B={(25*5)+(36-4)+71}/4, C=(128/4)*2. Write a program when A>B>C, shows true. In other cases, it shows false.

A.

public class Test
{
 public static void main(String[] args)
 {
  int A = ((25+5)+(36/4)-72)*5;
  int B = ((25*5)+(36-4)+71)/4;
  int C = (128/4)*2;
  
  boolean isTrue;
  
  isTrue = (A>B) && (B>C);
  System.out.println(isTrue);
 }
}

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Q. Write a program to show 2's complement of the digit 7.

A.

public class Test
{
 public static void main(String[] args)
 {
  int x=7;
  x = ~x;
  x = x+1;

  System.out.println(x);
 }
}

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Q. Write a program to check a third bit digit and fifth from left of an integer 15678.

A.

public class Test
{
 public static void main(String[] args)
 {
  int n=15678;
  System.out.println( (n>>2)&1 );
  System.out.println( (n>>4)&1 );
 }
}

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Q. The result of perator '<<' multiplies the operand by 2 times.
However, sometimes it changes MSB and shows wrong answers.
write an example using positive and negative integers to show the errors.

A.

public class Test
{
 public static void main(String[] args)
 {
  int num=7;
  int bitset = 1<<30;
  num |= bitset;
  System.out.println(num);
  System.out.println(num <<=1);
  
  num=-12;
  bitset = ~0;
  bitset ^= (1<<30);
  num &= bitset;
  System.out.println(num);
  System.out.println(num <<= 1);
 }
}