因为Java10发布所以学些Java8

前言

• 不知不觉间Java10TM都发布了，看了下新特性，好激动啊，然后回过头来继续工作，叹一口气，看着这个已经上线在改造过程中的Java7项目开始暗自神伤
• 总想找点代码来写，可是这些年太依赖客户了，客户不说，不要求，自己日常都不知道敲点什么，于是只能从最简单的模范，照搬开始了
• 在掘金上找些小Demo，一个个的试验完了，这里只留下源码，留给自己以后看下，留给你去搬运下，感受下函数式编程和流式API的体会了

Lambda

小实例

new Thread(()-> System.out.println("In Java8, Lambda expression rocks !!")).start();

语法

(params) -> expression
(params) -> statement
(params) -> { statements } 

列表迭代

List features = Arrays.asList("Lambdas", "Default Method", "Stream API", "Date and Time API");
//使用Lambda表达式
features.forEach(n -> System.out.println(n));
//使用方法引用
features.forEach(System.out::println);

filter

public class LamThread {
public static void main(String[] args) {
    List languages = Arrays.asList("Java", "Scala", "C++", "Haskell", "Lisp");
    System.out.println("Languages which starts with J :");
    streamFilter(languages,(str)->((String)str).startsWith("J"));
    streamFilter(languages,(str)->true);

}
public static void filter(List names, Predicate condition){
    for (String name:
         names) {
        if (condition.test(name)){
            System.out.println(name+"   ");
        }
    }
}

public static void streamFilter(List names,Predicate condition){
    names.stream().filter((name)->(condition.test(name))).forEach((name)->{
        System.out.println(name+"   ");
    });
}
}

StreamAPI的Map和Reduct方法

List costBeforeTax = Arrays.asList(100, 200, 300, 400, 500);
Object o = costBeforeTax.stream().map(
        (cost) -> (int) cost + (int) cost * .12
).reduce(
        (sum, cost) -> (double)sum + (double)cost).get();
System.out.println(o);

对列表每个单元应用函数

List G7 = Arrays.asList("USA", "Japan", "France", "Germany", "Italy", "U.K.","Canada");
    String collect = G7.stream().map(x -> x.toUpperCase()).collect(Collectors.joining(", "));
    System.out.println(collect);

复制不同的值，创建一个子列表

  List numbers = Arrays.asList(9, 10, 3, 4, 7, 3, 4);
  List integerList = numbers.stream().map(i -> i * i).distinct().collect(Collectors.toList());
  System.out.printf("原来是:%s,后来是 %s%n",numbers,integerList);