Question

Without using a computer determine the output for each of the loops.

1.
            int x = -2;
            while (x <= 2) {
                           System.out.println(x * x);
                           x = x + 1;
            }


2.
              int x = 1;
              int y = x;
            while (x <= 3) {
                           System.out.println(x + y);

                             y = x * 5;

                             x = x + 2;

              }

3.

              int x = 0;

              int y = -2;

              while (x <= 2) {

                             y = x * x + 1;

                             System.out.println(x + “, ” + y);

                             x = x + 1;

              }

4.

int x = 2;
              int y = x + 1;
            while (x <= 14) {
                           System.out.println(x – y);

                             y = x * 4;

                             x = x + 3;

              }

5. How many times will “Here” be printed?

              int x = 1;

              while (x <= 5) {

                             int y = 1;

                             while (y < 10){

                                           System.out.println(“Here”);

                                           y++;

                             }

x++;

              }            

6.

              int sum = 0;

              for (int i = 1; i <= 10; i++)

                             sum = sum + 1;

              System.out.println(sum);

7.

              for (int i = 0; i <=10; i += 2)

                             System.out.println(i * i);

8.

              for (int i = 6; i <= 11; i++) {

                             System.out.print(i + 3);

                             System.out.println(i);

}

9.

              for (int j = 15; j > 1; j--)

                             System.out.print(j);

10.         for (int i= 1; i <= 5; i++){

                             for( j=1; j <=3; j++)

                                           System.out.print(“*”);

                           System.out.println(“”);

}

Answer 1

(1) output :

4

1

0

1

4

Explanation : intitially x is -2 then we check if x is less than or equal to 2 since -2 is less than 2 , while loop starts and x*x is printed which is (-2)*(-2)=4 . Hence 4 is printed then we increment x by 1 so x becomes -2+1=-1

Then again while loop starts since -1 is less than 2, x*x= (-1*-1)=1.Hence 1 is printed then we increment x by 1 so x becomes -1+1=0

Then again while loop starts since 0 is less than 2, x*x= (0*0)=0.Hence 0 is printed then we increment x by 1 so x becomes 0+1=1

Then again while loop starts since 1 is less than 2, x*x= (1*1)=1.Hence 1 is printed then we increment x by 1 so x becomes 1+1=2

Then again while loop starts since 2 is equal to 2, x*x= (2*2)=4.Hence 4 is printed then we increment x by 1 so x becomes 2+1=3

Now since 3 is not less than or equal to 2 , while loop exits/stops executing.

(2) output :

2

8

Explanation : intitially x is 1 and we declare value of y equals to value of x , so y=1.Then we check if x is less than or equal to 3. since x=1 is less than 3 , while loop starts and prints (x+y)=1+1=2

Then we calculate y=x*5=1*5=5

And x=x+2=1+2=3

Now x=3,y=5

since x=3 is equal to 3 which is while loop condition , so while loop keeps running and x+y=3+5=8 is printed.

Then we calculate y=x*5=3*5=15

And x=x+2=3+2=5

Now x=5,y=15

since x=5 is not less than or equal to 3 which is while loop condition , so while loop exits i.e. we come out of while loop.

(3) output :

0,1

1,2

2,5

Explanation : intitially x is 0 and y is -2 .since x=0 is less than 2 which is while loop condition , while loop starts.

y is calculated as y=x*x+1=0*0+1=1

x,y is printed so 0,1 is printed since x=0 and y=1

x is again calculated as x=x+1=0+1=1 . so now x becomes x=1

since x=1 is less than 2 , while loop starts again ,

y is calculated as y=x*x+1=1*1+1=2

x,y is printed so 1,2 is printed since x=1 and y=2

x is again calculated as x=x+1=1+1=2 . so now x becomes x=2

since x=2 is equal to 2 , while loop starts again ,

y is calculated as y=x*x+1=2*2+1=5

x,y is printed so 2,5 is printed since x=2 and y=5

x is again calculated as x=x+1=2+1=3 . so now x becomes x=3

since x=3 is not less than or equal to 2 which is while loop condition , so while loop exits i.e. we come out of while loop.

(4) output :

-1

  -3

-12

-21

-30

Explanation : intitially x is 2 and y is x+1=2+1=3. since x=2 is less than 14 which is while loop condition , while loop starts.

(x-y) is printed which is (2-3)= -1

y is again recalculated as y=x*4=2*4=8

x is again recalculated as x=x+3=2+3=5

since x=5 is less than 14 , while loop starts again ,

(x-y) is printed which is (5-8)= -3

y is again recalculated as y=x*4=5*4=20

x is again recalculated as x=x+3=5+3=8

since x=8 is less than 14 , while loop starts again ,

(x-y) is printed which is (8-20)= -12

y is again recalculated as y=x*4=8*4=32

x is again recalculated as x=x+3=8+3=11

since x=11 is less than 14 , while loop starts again ,

(x-y) is printed which is (11-32)= -21

y is again recalculated as y=x*4=11*4=44

x is again recalculated as x=x+3=11+3=14

since x=14 is equal to 14 , while loop starts again ,

(x-y) is printed which is (14-44)= -30

y is again recalculated as y=x*4=14*4=56

x is again recalculated as x=x+3=14+3=17

since x=17 is not less than or equal to 14 which is while loop condition , so while loop exits i.e. we come out of while loop.

(5) output :

Here will be printed 45 times

Explanation : Here inner while loop will run 9 times since y=1 and inner while loop will run until y<10 so it will run 9 times.And outer while loop wil run 5 times since x=1 and outer while loop will run until x is less than or equal to 5.

so when first outer while loop starts , inner while loop will run 9 times

similary when 5 outer while loop runs. inner while loop will run 5*9=45 times , printing Here 45 times.

(6) output:

10

Explanation : intially sum is 0. for loop runs 10 times since i=1 and it checks if i<=10 .sum=sum+1 will be calculated 10 times. each time we update sum value and increment i

sum=0

when i =1 , sum=sum+1=0+1=1

when i =2 , sum=sum+1=1+1=2

when i =3 , sum=sum+1=2+1=3

when i =4 , sum=sum+1=3+1=4

when i =5 , sum=sum+1=4+1=5

when i =6 , sum=sum+1=5+1=6

when i =7 , sum=sum+1=6+1=7

when i =8 , sum=sum+1=7+1=8

when i =9 , sum=sum+1=8+1=9

when i =10 , sum=sum+1=9+1=10

Execution then stops since i=10 will be incremented to 11 and for loop condition is not met which is i<=10

(7) output :

0

4

16

36

64

100

Explanation :

when i =0 , i*i=0*0=0 is printed , i+=2 i.e i is incremented by 2 so i=0+2=2

when i =2 , i*i=2*2=4 is printed , i+=2 i.e i is incremented by 2 so i=2+2=4

when i =4 , i*i=4*4=16 is printed , i+=2 i.e i is incremented by 2 so i=4+2=6

when i =6 , i*i=6*6=36 is printed , i+=2 i.e i is incremented by 2 so i=6+2=8

when i =8 , i*i=8*8=64 is printed , i+=2 i.e i is incremented by 2 so i=8+2=10

when i =10 , i*i=10*10=100 is printed , i+=2 i.e i is incremented by 2 so i=10+2=12

Execution stops since i>10 now and for loop condition is not met which is i<=10

(8)

output :

96

107

118

129

1310

1411

Explanation :

when i =6 , i+3=6+3=9 is printed followed by i which is 6 so 96 will be printed on same line(Note- print command is used not println to print 9 so after printing 9 we will not go to next line) and  i is incremented by 1 so i=7

when i =7 , i+3=7+3=10 is printed followed by i which is 7 so 107 will be printed on same line(Note- print command is used not println to print 10 so after printing 10 we will not go to next line) and  i is incremented by 1 so i=8

when i =8 , i+3=8+3=11 is printed followed by i which is 8 so 118 will be printed on same line(Note- print command is used not println to print 11 so after printing 11 we will not go to next line) and  i is incremented by 1 so i=9

when i =9 , i+3=9+3=12 is printed followed by i which is 9 so 129 will be printed on same line(Note- print command is used not println to print 12 so after printing 12 we will not go to next line) and  i is incremented by 1 so i=10

when i =10 , i+3=10+3=13 is printed followed by i which is 10 so 1310 will be printed on same line(Note- print command is used not println to print 13 so after printing 13 we will not go to next line) and  i is incremented by 1 so i=11

when i =11 , i+3=11+3=14 is printed followed by i which is 11 so 1411 will be printed on same line(Note- print command is used not println to print 14 so after printing 14 we will not go to next line) and  i is incremented by 1 so i=12

Execution stops since i>11 now and for loop condition is not met which is i<=11

(9) output:

15141312111098765432

Explanation : intially j=15 and it is decremented by 1 after printing j until j is less than 1

so 15 then 14 then 13 then 12 so on will be printed untill it less than 1 i.e 2

We have used print command(not println) so output is printed on same line.

(10)output :

***

***

***

***

***

Note : here if you dont declare j as int then error will be thrown instead of above output

for( j=1; j <=3; j++) should be for(int j=1; j <=3; j++)

Explanation : Here i represents no of rows and j represents no of colums .

when i = 1 , inner loop will run 3 times printing * followed by space thrice since inner loop condition is j =1 and j<=3.

when i = 2 , inner loop will run 3 times printing * followed by space thrice since inner loop condition is j =1 and j<=3.

when i = 3 , inner loop will run 3 times printing * followed by space thrice since inner loop condition is j =1 and j<=3.

when i = 4 , inner loop will run 3 times printing * followed by space thrice since inner loop condition is j =1 and j<=3.

when i = 5 , inner loop will run 3 times printing * followed by space thrice since inner loop condition is j =1 and j<=3.

so total 5 rows will be printed and in each row there will be stars followed by space combination printed thrice