Loops

Loops are useful if you want to do the operation multiple times or if you want to do a operation for each element in a list.

While loop

A simple while loop looks like this:

groovy

while (condition) {
    operation
}

The condition is a boolean. As long as that condition evaluates to true, the operation will be executed.

Example

This will print 0, 1, 2, 3, 4, 5, 6, 7, 8, 9.

groovy

int i = 0;
while (i < 10) {
    print("${i++}, ")
}

There is also a do while loop which ignores the condition on its first run.

groovy

do {
    operation
} while (condition)

For loop

For loops are similar to while loops.

groovy

for(init; condition; incrementor) {
    operation
}

init is called before the loop. condition is checked before each run and incrementor is called after each run.

Example

This will print 0, 1, 2, 3, 4, 5, 6, 7, 8, 9.

groovy

for(int i = 0; i < 10; i++) {
    print("${i++}, ")
}

Enhanced for loop

Those are very useful for lists and maps. This will print Hello world!

groovy

def list = ['He', 'llo', ' w', 'or', 'ld!']
for(part in list) {
    print(part)
}

part creates a new variable on each run for the current element in the list lists.

For maps, it looks like this

groovy

def elements = [
        'Au': 'Gold',
        'Ag': 'Silver',
        'Pb': 'Lead',
        'H' : 'Hydrogen'
]
// prints al elements
for (entry in elements) {
    println("${entry.key}: ${entry.value}")
}

Control flow in loops

break can be used at any time inside a loop to abort the current and all following runs. continue will only abort the current run and continues with the next run (if the condition is still true)