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

The output for the given loops:

1) int x = -2;

while (x <= 2) {

System.out.println(x * x);

x = x + 1;

}

Solution:

Iteration Number	x	x<=2	Println(x*x)	x=x+1
1st	-2	-2<=2          True	-2* -2 = 4	x= -2+1 = -1
2nd	-1	-1<=2           True	-1 * -1 =1	x=-1 + 1 =0
3rd	0	0<=2           True	0*0=0	x=0+1=1
4th	1	1<=2           True	1*1 =1	x=1+1=2
6th	2	2<=2           True	2*2=4	x=2+1=3
7th	3	3<=2             False	Will not execute	Will not execute

Output :

4

1

0

1

4

2) int x = 1;

int y = x;

while (x <= 3) {

System.out.println(x + y);

y = x * 5;

x = x + 2;

}

Solution:

  

Iteration Number	x	y	x<=3	Println(x+y)	y=x*5	x=x+2
1st	1	1	1<=3   True	1+1=2	1*5=5	1+2=3
2nd	3	5	3<=3      True	3+5=8	3*5=15	3+2=6
3rd	6	15	6 <=3       False	Will not execute	Will not execute	Will not execute

Output :

2

8

3) int x = 0;

int y = -2;

while (x <= 2) {

y = x * x + 1;

System.out.println(x + “, ” + y);

x = x + 1;

}

Solution:

Iteration Number	x	y	x<=2	y=x*x+1	Print(x+”,”+y)	x=x+1
1st	0	-2	0<=2 True	0*0+1=1	0 , 1	0+1=1
2nd	1	1	1<=2 True	1*1+1=2	1 , 2	1+1=2
3rd	2	2	2<=2 True	2*2+1=5	2 , 5	2+1=3
4th	3	5	3<=2 False	Will not execute	Will not execute	Will not execute

Output:

0 , 1

1 , 2

2 , 5

4) int x = 2;

int y = x + 1;

while (x <= 14) {

System.out.println(x – y);

y = x * 4;

x = x + 3;

}

Solution:

Iteration Number	x	y	x<=14	Println(x-y)	y=x*4	x=x+3
1st	2	3	2<=14 True	2-3= -1	2*4=8	2+3=5
2nd	5	8	5<=14 True	5-8= -3	5*4=20	5+3=8
3rd	8	20	8<=14 True	8-20= -12	8*4=32	8+3=11
4th	11	32	11<=14 True	32-11= -21	11*4=44	11+3=14
6th	14	44	14<=14 True	14-44= -30	14*4=56	14+3=17
7th	17	56	17<=14 False	Will not execute	Will not execute	Will not execute

Output:

-1

-3

-12

-21

-30

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++;

}

Solution:

Here the Outer loop gets excuted for 5 times and the inner loop gets executed for 9 times . The Inner while loop is used to print "Here" 9 times . The outer while is used to print these 9 "Here" 5 times.

As soon the condtion for the inner while loop becomes false i.e when y becomes 10 then it comes out of the loop and the outer loop is executed again.

The execution happens like this:

1st Iteration: The outer while loop gets executed 1st time when x=1 and the inner for loop gets executed while y=1,2.....9 and prints "Here "9 times one below the other.

2nd Iteration:The outer while loop gets executed 2nd time when x=2 and the inner for loop gets executed while y=1,2.....9 and prints "Here" 9 times one below the other.

3rd Iteration:The outer while loop gets executed 3rd time when x=3 and the inner for loop gets executed while y=1,2.....9 and prints "Here" 9 times one below the other.

4th Iteration:The outer while loop gets executed 4th time when x=4 and the inner for loop gets executed while y=1,2.....9 and prints "Here" 9 times one below the other.

5th Iteration:The outer while loop gets executed 5th  time when x=5 and the inner for loop gets executed while y=1,2.....9 and prints "Here" 9 times one below the other.

6th Iteration:The condition of the outer loop becomes false i.e i=6 hence it comes out of the loop .

As the outer loop is excuted 5 times and inner loop 9 times so 'Here' gets printed 45 times each 'Here' on next line.

Output:

"Here" is printed 45 times on separate lines.

6) int sum = 0;

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

sum = sum + 1;

System.out.println(sum);

Solution:

Iteration Number	sum	i	i<=10	sum=sum+1	i++
1st	0	1	1<=10 True	0+1=1	2
2nd	1	2	2<=10 True	1+1=2	3
3rd	2	3	3<=10 True	2+1=3	4
4th	3	4	4<=10 True	3+1=4	5
5th	4	5	5<=10 True	4+1=5	6
6th	5	6	6<=10 True	5+1=6	7
7th	6	7	7<=10 True	6+1=7	8
8th	7	8	8<=10 True	7+1=8	9
9th	8	9	9<=10 True	8+1=9	10
10th	9	10	10<=10 True	9+1=10	11
11th	10	11	11<=10 False	Will not execute	Will not execute

The final Sum value will be printed as output.

Output:

10

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

System.out.println(i * i);

Solution:

Iteration Number	i	i<=10	Println(i*i)	i+=2
1st	0	0<=10 True	0*0=0	0+2=2
2nd	2	2<=10 True	2*2=4	2+2=4
3rd	4	4<=10 True	4*4=16	4+2=6
4th	6	6<=10 True	6*6=36	6+2=8
6th	8	8<=10 True	8*8=64	8+2=10
7th	10	10<=10 True	10*10=100	10+2=12
8th	12	12<=10 False	Will not execute	Will not execute

Output:

0

4

16

36

64

100

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

System.out.print(i + 3);

System.out.println(i);

}

Solution:

Iteration Number	i	i<=11	Print(i+3)	Println(i)	i++
1st	6	6<=11 True	6+3=9	6	7
2nd	7	7<=11 True	7+3=10	7	8
3rd	8	8<=11 True	8+3=11	8	9
4th	9	9<=11 True	9+3=12	9	10
6th	10	10<=11 True	10+3=13	10	11
7th	11	11<=11 True	11+3=14	11	12
8th	12	12<=11 False	Will not execute	Will not execute	Will not execute

note:Here print will print the output on same line i.e 9 and println will move to the next line after printing the output on the same line so it becomes 96 and when next time it prints 10 it starts on next line.

Output:

96

107

118

129

1310

1411

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

System.out.print(j);

Solution:

Here the for loop gets executed until the condtion becomes false . Now j =15 and after every iteration the value of j is decremented by 1 i.e j =14 then j=13 so this will continue unt