java-lambda簡化寫法整理

lambda寫法

//lambda 函數編程 替代匿名接口實現 //()參數列表 ->連接符 {方法體}

//接口中只許有一個需要實現的接口

1. 簡寫多線程-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.接口實現方法簡化

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簡化

1.javabean類實現
@Override
 public int compareTo(UserBean o) {
  // TODO Auto-generated method stub
  return o.getAge()-this.getAge();
 }
2.調用sort時實現
 List<UserBean> llBeans = new ArrayList<UserBean>();
llBeans.add(new UserBean(18,"James"));
llBeans.add(new UserBean(22,"Sally"));
​
//調用時實現排序
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());   
​

4.參數省略問題，更加省略寫法

• 1.參數列表小括號參數類型可以省略

• 2.參數列表小括號只有一個參數，括號可以省略

• 3.大括號如果也只有一句話，大括號可以省略，return 分號可以省略

   

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

5.循環簡化

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迭代簡化

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迭代簡化

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

8.Set迭代簡化

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);
}