循环和输出

Question

This is a homework question that I cannot figure out. It's in Java.

Suppose we want to write a for loop that produces the following nine lines of output:

 4:
 8:
12:
16:
20:
24:
28:
32:
36:

Suppose we will use the following for-loop to produce the output:

int index;
for (index = __A__; __B__ ; __C__ ) {
    System.out.printf(__D__, index);
}

Answer what should be in the four blanks in each of the following for the code?

1. _ _ A _ _
2. _ _ B _ _
3. _ _ C _ _
4. _ _ D _ _

Answer 1

int index;
for (index = __A__; __B__ ; __C__ ) {
    System.out.printf(__D__, index);
}

If you see the output, the number (index) starts with 4.

Therefore, A : 4

It ends at 36.

Therefore, B : index<=36

It increases by 4.

Therefore, C : index+=4

Printed line's format is D : "%2d:\\n"

Answer 2

This for loop will give you the answer:

for (index=4; index<=36; index+=4) {
    System.out.printf(":\n"+ index);
}

A is index = 4

B is index<=36

C is index+=4

D is ":\\n"

Make the print statement as:

System.out.printf(index + ":\n");

Now you will get the exact answer you expect.