Loops
Loops are useful if you want to do the operation multiple times or if you want to do an operation for each element in a list.
While loop
A simple while loop looks like this:
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.
int i = 0;
while (i < 10) {
print("${i++}, ")
}There is also a do while loop which ignores the condition on its first run.
do {
operation
} while (condition)For loop
For loops are similar to while loops.
for(init; condition; incrementor) {
operation
}init is called before the loop. condition is checked before each run and incrementor is called after each run.
Example
This will print 0, 1, 2, 3, 4, 5, 6, 7, 8, 9.
for(int i = 0; i < 10; i++) {
print("${i++}, ")
}Enhanced for loop
Those are very useful for lists and maps. This will print Hello world!
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
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)
Count
There are multiple different strategies to iterate through a loop a specific number of times.
def x = 0
while (x < 10) {
log.info x++
}def x = 0
do {
log.info x++ // this would execute at least once, even if x was greater than 10
} while (x < 10)for (def x = 0; x < 10; x++) {
log.info x
}for (def x in [0, 1, 2, 3, 4, 5, 6, 7, 8, 9]) {
log.info x
}
for (def x : [0, 1, 2, 3, 4, 5, 6, 7, 8, 9]) { // "in" and ":" are the same here
log.info x
}[0, 1, 2, 3, 4, 5, 6, 7, 8, 9].each {
log.info x
}for (def x : 0..<10) { // creates a range
log.info x
}(0..<10).each {
log.info x
}
Waiting Idly
Nullpinter