How can I terminate a loop for input if I don't know the number of lines beforehand?

Question

How can I terminate a loop for input if I don't know the number of lines beforehand?

2015-08, 2016-04

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I have tried this
while (reader.hasNextLine()) but it is expecting another input.

Answer 1

You can break any loop in java using break keyword, in case of while loop:

while((reader.hasNextLine()) {
   boolean shouldBreak = ... // your code when it should break
   if (shouldBreak) break;

}
// here the execution will go after the loop

The break can be used in any loop like for/while/do.

Answer 2

while(true) { //or any other condition
    //do something
    if (userInput.equals("&") {
        break;
    }
}

break keyword can be used for immediate stopping and escaping the loop. It is used in most of programming languages. There is also one useful keyword to slightly influence loop processing: continue . It immediately jumps to the next iteration.

Examples :

int i = 0;
while (true) {
    if (i == 4) {
        break;
    }
    System.out.println(i++);
}

will print:

0
1
2
3

Continue:

int i = 0;
while (true) {
    if (i == 4) {
        i++;
        continue;
    }
    if (i == 6) {
        break;
    }
    System.out.println(i++);
}

will print:

0
1
2
3
5