CODEWITHSUNDEEP
javacfor-loopiteration
Sana
Sana

Reputation: 118

Is there any difference between for loop in java and c?

for loop in c

int i;
int n = 20;
for(i = 0; i + n; i-- ) {
     printf("-\n");

}

for loop in java

int i;
int n=20;
for (i = 0; i + n; i--) {
   System.out.println("-\n");
}

In the above example for loop in c is working fine(will print "-" 20 times).But for loop in java shows error as

Exception in thread "main" java.lang.Error: Unresolved compilation problem: Type mismatch: cannot convert from int to boolean

why it shows this kind of error?

Upvotes: 3

Views: 3071

Answers (2)

Luiggi Mendoza
Luiggi Mendoza

Reputation: 85779

In C, 0 is considered false and the rest of number are interpreted as true. In Java, this doesn't work since it has a boolean type that is not an int, and an int cannot be directly converted into a boolean.

To fix the Java code, you should write the second part as a boolean expression:

for (i = 0; (i + n) != 0; i--) {
    System.out.println("-\n");
}

While (i + n) != 0 may work, I would prefer to use (i + n) > 0, because if n starts at -1, this loop will work until i goes down to Integer.MIN_VALUE value, underflows to Integer.MAX_VALUE and go down to 1. To prevent that behavior (in case is undesired), it would be better to write it like this:

for (i = 0; (i + n) > 0; i--) {
    System.out.println("-\n");
}

From @Lundin's comment, looks like your C code should be fixed as well:

//or use my proposed fix by using > rather than !=
for(i = 0; (i + n) != 0; i-- ) {
    printf("-\n");
}

Upvotes: 10

Dawood ibn Kareem
Dawood ibn Kareem

Reputation: 79838

The original version of C didn't have booleans, so everyone used integers instead. The language would interpret anything non-zero as true, and zero as false.

But Java is stricter about what's a boolean and what's an integer - you actually need to use a boolean expression (such as i + n != 0) to check whether the loop should continue.

Upvotes: 3

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