1.用lambda表達式實現(xiàn)map
List cost = Arrays.asList(10.0,20.0,30.0);
cost.stream().forEach(x-> System.out.println(x));
System.out.println("----------");
cost.stream().map(x -> x + x*0.05).forEach(x -> System.out.println(x));
2.?用lambda表達式對集合進行迭代
List languages = Arrays.asList("java","scala","python");
//before java8
for(String each:languages) {
System.out.println(each);
}
System.out.println("-------");
//after java8
languages.forEach(x -> System.out.println(x));
languages.forEach(System.out::println);
3.用lambda表達式實現(xiàn)map與reduce
//map+reduce+lambda表達式
List cost = Arrays.asList(10.0, 20.0,30.0);
?double allCost = cost.stream().map(x -> x+x*0.05).reduce((sum,x) -> sum + x).get();
System.out.println(allCost);//63.0
等同于：
List cost = Arrays.asList(10.0, 20.0,30.0);
? ? ? ? double sum = 0;
? ? ? ? for(double each:cost) {
? ? ? ? ? ? each += each * 0.05;
? ? ? ? ? ? sum += each;
? ? ? ? }
? ? ? ? System.out.println(sum);//63.0
4.filter操作
List cost = Arrays.asList(10.0,20.0,30.0,40.0);
List filteredCost = cost.stream().filter(x -> x >25.0).collect(Collectors.toList());
filteredCost.forEach(x -> System.out.println(x));//30.0? 40.0
5.與函數(shù)式接口Predicate配合
public static void filterTest(List languages, Predicate condition) {
? ?languages.stream().filter(x -> condition.test(x)).forEach(x -> System.out.println(x + " "));? ?
?}
public static void main(String[] args) {
List languages = Arrays.asList("Java","Python","scala","Shell","R"); ? ? ? ? ? ? System.out.println("Language starts with J: ");? ? ? ??
filterTest(languages,x -> x.startsWith("J"));? ? ? ??
System.out.println("\nLanguage ends with a: ");? ? ? ??
filterTest(languages,x -> x.endsWith("a"));? ? ? ??
System.out.println("\nAll languages: ");? ? ? ??
filterTest(languages,x -> true);? ? ? ??
System.out.println("\nNo languages: ");? ? ? ?
?filterTest(languages,x -> false);? ? ? ??
System.out.println("\nLanguage length bigger three: ");? ? ? ??
filterTest(languages,x -> x.length() > 4);? ?
?}
返回結(jié)果：
Language starts with J:
Java
Language ends with a:
Java
scala
All languages:
Java
Python
scala
Shell
R
No languages:
Language length bigger three:
Python
scala
Shell
6.替代匿名內(nèi)部類
new Thread(new Runnable() {
? ? ? ? ? ? @Override? ? ? ? ? ? public void run() {
? ? ? ? ? ? ? ? System.out.println("The old runable now is using!");
? ? ? ? ? ? }
? ? ? ? }).start();
等同于
new Thread(() -> System.out.println("It's a lambda function!")).start();
