1 |
if ( ... ) { |
2 |
... |
3 |
} else if (...) { |
4 |
... |
5 |
} else { |
6 |
... |
7 |
} |
三元操做符
Groovy 也支持Java傳統的三元操做符：ruby
1 |
def y = 5 |
2 |
def x = (y > 1) ? "worked" : "failed" |
3 |
assert x == "worked" |
switch
Groovy也支持switch語句，不過和java的switch語句仍是有很大的區別的：閉包
1 |
def x = 1.23 |
2 |
def result = "" |
3 |
4 |
switch ( x ) { |
5 |
case "foo": |
6 |
result = "found foo" |
7 |
// lets fall through |
8 |
9 |
case "bar": |
10 |
result += "bar" |
11 |
12 |
case [4, 5, 6, 'inList']: |
13 |
result = "list" |
14 |
break |
15 |
16 |
case 12..30: |
17 |
result = "range" |
18 |
break |
19 |
20 |
case Integer: |
21 |
result = "integer" |
22 |
break |
23 |
24 |
case Number: |
25 |
result = "number" |
26 |
break |
27 |
28 |
default: |
29 |
result = "default" |
30 |
} |
31 |
32 |
assert result == "number" |
從上面的例子能夠看出switch ( x )中的x能夠使用任何類型的值，並且下面的匹配值也能夠使用任何的類型。spa
循環
Groovy也支持Java傳統的while循環語法：code
1 |
def x = 0 |
2 |
def y = 5 |
3 |
4 |
while ( y-- > 0 ) { |
5 |
x++ |
6 |
} |
7 |
8 |
assert x == 5 |
for循環
在Groovy中，for循環更加的簡單，並且若是你願意的話，你也能夠在Groovy中使用標準的C/Java的for循環語法。blog
1 |
for (int i = 0; i < 5; i++) { |
2 |
} |
3 |
4 |
// iterate over a range |
5 |
def x = 0 |
6 |
for ( i in 0..9 ) { |
7 |
x += i |
8 |
} |
9 |
assert x == 45 |
10 |
11 |
// iterate over a list |
12 |
x = 0 |
13 |
for ( i in [0, 1, 2, 3, 4] ) { |
14 |
x += i |
15 |
} |
16 |
assert x == 10 |
17 |
18 |
// iterate over an array |
19 |
array = (0..4).toArray() |
20 |
x = 0 |
21 |
for ( i in array ) { |
22 |
x += i |
23 |
} |
24 |
assert x == 10 |
25 |
26 |
// iterate over a map |
27 |
def map = ['abc':1, 'def':2, 'xyz':3] |
28 |
x = 0 |
29 |
for ( e in map ) { |
30 |
x += e.value |
31 |
} |
32 |
assert x == 6 |
33 |
34 |
// iterate over values in a map |
35 |
x = 0 |
36 |
for ( v in map.values() ) { |
37 |
x += v |
38 |
} |
39 |
assert x == 6 |
40 |
41 |
// iterate over the characters in a string |
42 |
def text = "abc" |
43 |
def list = [] |
44 |
for (c in text) { |
45 |
list.add(c) |
46 |
} |
47 |
assert list == ["a", "b", "c"] |
閉包(closures)
有時候你也能夠使用閉包的each()和eachWithIndex()方法來替換一些for循環代碼。string
1 |
def stringList = [ "java", "perl", "python", "ruby", "c#", "cobol", |
2 |
"groovy", "jython", "smalltalk", "prolog", "m", "yacc" ]; |
3 |
4 |
def stringMap = [ "Su" : "Sunday", "Mo" : "Monday", "Tu" : "Tuesday", |
5 |
"We" : "Wednesday", "Th" : "Thursday", "Fr" : "Friday", |
6 |
"Sa" : "Saturday" ]; |
7 |
8 |
stringList.each() { print " ${it}" }; println ""; |
9 |
// java perl python ruby c# cobol groovy jython smalltalk prolog m yacc |
10 |
11 |
stringMap.each() { key, value -> println "${key} == ${value}" }; |
12 |
// Su == Sunday |
13 |
// We == Wednesday |
14 |
// Mo == Monday |
15 |
// Sa == Saturday |
16 |
// Th == Thursday |
17 |
// Tu == Tuesday |
18 |
// Fr == Friday |
19 |
20 |
stringList.eachWithIndex() { obj, i -> println " ${i}: ${obj}" }; |
21 |
// 0: java |
22 |
// 1: perl |
23 |
// 2: python |
24 |
// 3: ruby |
25 |
// 4: c# |
26 |
// 5: cobol |
27 |
// 6: groovy |
28 |
// 7: jython |
29 |
// 8: smalltalk |
30 |
// 9: prolog |
31 |
// 10: m |
32 |
// 11: yacc |
33 |
34 |
stringMap.eachWithIndex() { obj, i -> println " ${i}: ${obj}" }; |
35 |
// 0: Su=Sunday |
36 |
// 1: We=Wednesday |
37 |
// 2: Mo=Monday |
38 |
// 3: Sa=Saturday |
39 |
// 4: Th=Thursday |
40 |
// 5: Tu=Tuesday |
41 |
// 6: Fr=Friday |
從if-else和try-catch代碼塊中返回值
從 Groovy 1.6開始，在方法或者閉包中的最後一行表達式，能夠從if/else和try/catch/finally代碼塊中返回值，並且並不須要明確的使用return關鍵字返回值，只須要他們是代碼塊的最後一個表達式就行。it
下面的例子就說明了這個狀況，在下面的代碼塊中雖然沒有顯示的調用return關鍵字，可是仍然會返回1：
1 |
def method() { |
2 |
if (true) 1 else 0 |
3 |
} |
4 |
5 |
assert method() == 1 |
對於 try/catch/finally blocks代碼塊來講，若是try代碼塊中沒有拋出異常的話，那麼try代碼塊的最後一行的表達式將會被返回，若是try的代碼塊拋出異常而且被catch住的時候，那麼catch代碼塊中的最後一個表達式的值將會被返回。
可是請注意：finally代碼塊不會返回值的。
1 |
def method(bool) { |
2 |
try { |
3 |
if (bool) throw new Exception("foo") |
4 |
1 |
5 |
} catch(e) { |
6 |
2 |
7 |
} finally { |
8 |
3 |
9 |
} |
10 |
} |
11 |
12 |
assert method(false) == 1 |
13 |
assert method(true) == 2 |