lambda写法

//lambda 函数编程 替代匿名接口实现 //()参数列表 ->连接符 {方法体}

//接口中只许有一个需要实现的接口

1. 简写多线程-run方法

new Thread(new Runnable() {
            @Override
            public void run() {
                System.out.println(Thread.currentThread().getName());
            }
        }).start();
        
//lambda
new Thread(()->{
    System.out.println(Thread.currentThread().getId());
}).start();
​
new Thread(()->{System.out.println(Thread.currentThread().getName());}).start();
new Thread(()->System.out.println(Thread.currentThread().getName())).start();
​

2.接口实现方法简化

public static void testPerson(Iperson person) {
        System.out.println(person.eat("test"));
    }
    
    public static void main(String[] args) {
        testPerson(new Iperson() {
            @Override
            public int eat(String food) {
                // TODO Auto-generated method stub
                return 1;
            }
        });
        
        testPerson((String food)->{return 2;});
        testPerson(food->2);

3.List-sort简化

1.javabean类实现
@Override
    public int compareTo(UserBean o) {
        // TODO Auto-generated method stub
        return o.getAge()-this.getAge();
    }
2.调用sort时实现
    List<UserBean> llBeans = new ArrayList<UserBean>();
llBeans.add(new UserBean(18,"James"));
llBeans.add(new UserBean(22,"Sally"));
​
//调用时实现排序
Collections.sort(llBeans,new Comparator<UserBean>() 
                 {
                     @Override
                     public int compare(UserBean o1, UserBean o2) {
                         // TODO Auto-generated method stub
                         return o1.getAge()-o2.getAge();
                     }
                 });
//lambda
Collections.sort(llBeans, (o1,o2)->{return o2.getAge()-o1.getAge();});
for (UserBean userBean : llBeans) {
    System.out.println(userBean);
}
Collections.sort(llBeans,(o1,o2)->o2.getAge()-o1.getAge());         
​

4.参数省略问题，更加省略写法

  • 1.参数列表小括号参数类型可以省略

  • 2.参数列表小括号只有一个参数，括号可以省略

  • 3.大括号如果也只有一句话，大括号可以省略，return 分号可以省略

     

new Thread(()->System.out.println(Thread.currentThread().getName())).start();
testPerson(food->2);     
Collections.sort(llBeans,(o1,o2)->o2.getAge()-o1.getAge());

5.循环简化

List<TestList> list = new ArrayList<TestList>();
list.add(new TestList("aa", 1));
list.add(new TestList("bb", 0));
​
Collections.sort(list, (o1,o2)->o1.getOrderNo()-o2.getOrderNo());
​
for (TestList ll : list) {
    System.out.println(ll);
}
​
list.forEach((TestList ll)->{System.out.println(ll);});
list.forEach(d->System.out.println(d));

6.Map迭代简化

Map<String, Object> map = new TreeMap<String, Object>();
map.put("aa", 11);
map.put("bb",22);
for (Map.Entry<String, Object> entry : map.entrySet()) {
System.out.println(entry.getKey()+":"+entry.getValue());
}
​
for (String key : map.keySet()) {
System.out.println(key+"::"+map.get(key));
}
​
map.forEach((key,value)->System.out.println(key+"="+value));
​
map.forEach((key,value)->{System.out.println(key+"=="+value);});

7.List迭代简化

llBeans.forEach(u->System.out.println(u));

8.Set迭代简化

Set<String> ss = new TreeSet<String>();
ss.add("abc");
ss.add("edf");
ss.forEach(s->System.out.println(s));
for (String string : ss) {
System.out.println(string);
}