CODEWITHSUNDEEP
javafor-loopboolean
topacoBoy
topacoBoy

Reputation: 197

Boolean in FOR loop

I don't understand this code. One of my friend thought me to use the boolean to make it work. I don't really understand when he explains it. Why is the found in the for loop?

int id = input.nextInt();   
boolean found = false;
for (int i = 0; i < z && !found; i++){
    if (arr[i].getId() == id){
        found = true;
        index = i;
    }   
}

Upvotes: 2

Views: 27523

Answers (3)

Justin
Justin

Reputation: 2031

The conditional statement inside the for loop reads

i < z && !found

When 'found' is true, the for loop will stop looping. You can read more about for loops here

For loop syntax looks like this:

for (initialize ; condition ; increment) {}

It's also possible to replace your for loop with a while loop.

int i = 0;
int found = false;
while(i < z && !found) {
    if(arr[i].getId()==id){
        found = true;
        index = i;
    }
}

In both cases, you can simplify your conditional using the "break" keyword. The break keyword causes a loop to exit immediately. This may or may not be the appropriate solution here, but it does show another way to handle these kinds of loops.

for(int i=0; i<z; i++){
    if(arr[i].getId()==id){
        index = i;
        break;
    }   
}

Upvotes: 1

Eran
Eran

Reputation: 393781

The i<z && !found part of the for loop is the condition, which must be true in order for the loop to continue. Adding the !found part means that the loop would terminate when either found is true or i>=z, whichever happens first. Without that condition, the loop would always run z times, even if a match (i.e. arr[i].getId()==id) is found on the first iteration. Therefore, this condition is an optimization that reduces the running time of the loop.

An alternative to the !found condition is using the break keyword to terminate the loop :

            for(int i=0; i<z; i++){
                if(arr[i].getId()==id){
                    found = true;
                    index = i;
                    break;
                }   
            }

Upvotes: 0

Saiful Islam Rana
Saiful Islam Rana

Reputation: 11

Here "Boolean" is using to terminate the loop as soon as the inputted "id" found in your array. The good thing is the compiler don't have to search until last index wheres "id" already found.

Upvotes: 1

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