Groovy学习笔记-Java 5新特性支持

1.枚举enum

enum CoffeeSize{
    SHORT,
    SMALL,
    MEDIUM,
    LARGE,
    MUG
}

def orderCoffee(size){
    print "Coffee order received for size $size:"
    switch(size){
        case [CoffeeSize.SHORT, CoffeeSize.SMALL]:
            println 'Conscious'
            break;
        case CoffeeSize.MEDIUM..CoffeeSize.LARGE:
            println 'Programmer'
            break;
        case CoffeeSize.MUG:
            println 'Caffeine IV'
            break;
    }
}

orderCoffee(CoffeeSize.SMALL)
orderCoffee(CoffeeSize.LARGE)
orderCoffee(CoffeeSize.MUG)

for(size in CoffeeSize.values()){
    println size
}

/*output
Coffee order received for size SMALL:Conscious
Coffee order received for size LARGE:Programmer
Coffee order received for size MUG:Caffeine IV
SHORT
SMALL
MEDIUM
LARGE
MUG
*/

2.for-each循环

def list = [1,3,6,4,9]

println '传统for循环'
for(int i = 0; i < list.size(); i++){
    println i
}

println '实现了 Iterable接口的for循环'
for(int i : list){
    println i
}

println '不指定类型的for循环'
for(i in list){
    println i
}
/*output
传统for循环
0
1
2
3
4
实现了 Iterable接口的for循环
1
3
6
4
9
不指定类型的for循环
1
3
6
4
9

*/

3.变长参数

def receiveVarArgs(int a, int...b){
    println "$a and $b"
}

def receiveArray(int a, int[] b){
    println "$a and $b"
}

receiveVarArgs(1,2,3,4,5)

receiveArray(1,2,3,4,5)

/*output
1 and [2, 3, 4, 5]
1 and [2, 3, 4, 5]
*/

4.注解-@Delegate

class Worker{
    def Work(){println 'Work'}
    def Analyze(){println 'Analyze'}
    def WriteReport(){println 'WriteReport'}
}

class Expert{
    def Analyze(){println 'Expert Analyze'}
}

class Manager{
    @Delegate Expert expert = new Expert()
    @Delegate Worker worker = new Worker()
}

def ironcrow = new Manager()
ironcrow.Work()
ironcrow.Analyze()
ironcrow.WriteReport()

/*output
Work
Expert Analyze
WriteReport

*/

5-注解@Lazy：惰性创建

// 非惰性创建
class Heavy {
    def size = 10
    Heavy(){
        println("Create Heavy with $size")
    }
}

class AsNeeded {
    def value
     Heavy heavy1 = new Heavy()
     Heavy heavy2 = new Heavy(size: value)

    AsNeeded(){
        println 'Created AsNeeded'
    }
}

class Program {
    static void main(String[] args){
        def asNeeded = new AsNeeded(value: 1000)
        println asNeeded.heavy1.size
        println asNeeded.heavy1.size
        println asNeeded.heavy2.size
        println asNeeded.heavy2.size
    }
}

/*output

Create Heavy with 10
Create Heavy with 10
Created AsNeeded
10
10
null
null
*/

// 惰性创建
class AsNeeded {
    def value
    @Lazy Heavy heavy1 = new Heavy()
    @Lazy Heavy heavy2 = new Heavy(size: value)

    AsNeeded(){
        println 'Created AsNeeded'
    }
}

/*output
Created AsNeeded
Create Heavy with 10
10
10
Create Heavy with 10
1000
1000
*/

6.@Singleton单例

@Singleton(lazy = true)
class TheUnique{
    def sayHello(){
        println 'hello'
    }
}

TheUnique.instance.sayHello()

/*output
hello
*/