To execute a block of code once or a multiple times based on a condition, you would need Control structures. Groovy supports the usual
- Conditional statements:
if-else, "nested" if then else if, switch, try-catch-finally - Looping statements:
for, for in, while loop - Branching statements:
break, continue, return
See here for more information on the Control structures.
On this page:
Table of Contents
Conditional statements
Conditional statements execute a set of statements only if the condition is true
...
| Code Block | ||||
|---|---|---|---|---|
| ||||
def x = 2
//Simple if
if(x==2){
false
}
//Simple if else
if(x == 2){
x = x + 2
}
else{
x = x - 2
}
//Nested if
if (x) {
x = x + 1
} else if (y) {
y = y + 1
} else {
0
}
//Assign and test in nested expression
if ((x = 3)) {
return true
}
//Optional return statement
def sysName = "Windows"
if (sysName.contains("Windows"))
"We're on Windows."
else
"Oh, well we are on Mac" |
Switch statement
The switch statement executes one statement from multiple conditions. It is like if-else-if ladder statement. The switch statement in Groovy can handle any kind of switch value and different kinds of matching can be performed.
| Code Block | ||||
|---|---|---|---|---|
| ||||
def a = 1
def log = ""
switch (a) {
case 0 : log += "0" //|#1 fall
case "Demo" : log += "Demo" //String
case [2,3,5] : log += 5
case 5..10 : log += "Range"
case 1 : log += "1" //|#1 through
case 2 : log += "2"; break
default : log += 'default'
}
log == "125Range12" //returns true |
try-catch-finally
...
| Code Block | ||||
|---|---|---|---|---|
| ||||
def myMethod() {
throw new IllegalArgumentException()
}
def log = []
try {
myMethod()
} catch (Exception e) {
log << e.toString()
} finally {
log << "finally"
}
log.size() == 2 //returns true |
Looping statements
Looping repeats the execution of a block of code multiple times. The loops available in Groovy are:
while loop
In a while loop the boolean test is evaluated, and if it's true, the body of the loop is then executed.
| Code Block | ||||
|---|---|---|---|---|
| ||||
def list = [1, 2, 3]
while (list){
list.remove(0)
}
list // returns [] |
Note: There is no do-while loop in Groovy
for/for-in loop
for / for-in loop is used to iterate a part of the program several times. If the number of iteration is fixed, it is recommended to use the for loop. In Groovy the for loop is much simpler and works with any kind of array, collection, Map, etc.
| Code Block | ||||
|---|---|---|---|---|
| ||||
// Normal for loop
def x = 0
for (i = 0; i < 5; i++) {
x += i;
}
x == 10 //returns true
// iterate over a range
def x = 0
for ( i in 0..9 ) {
x += i
}
x == 45 //returns true
// iterate over an array
def array = (0..4).toArray()
x = 0
for ( i in array ) {
x += i
}
x == 10 //returns true
//iterate over a list
def x = 0
def list = [10,12,13,14];
for(j in list){
x += j;
}
x == 49 //returns true
//iterate over a map
def x = 0
def customers = [
0 : "David",
1 : "Elle",
2 : "Peaches"
];
for(cust in customers){
x += cust.key
}
x == 3 //returns true
//iterate over values of a Map
def x = ""
def customers = [
0 : "David",
1 : "Elle",
2 : "Peaches"
];
for(cust in customers){
x += cust.value
x += ","
}
x == "David,Elle,Peaches" //returns true
// iterate over the characters in a string
def text = "abc"
def list = []
for (c in text) {
list.add(c)
}
list == ["a", "b", "c"] //returns true |
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