Java 5 新特性

1.自动装箱、拆箱

/**
 * 自动装箱、拆箱
 *
 * @author GaoHangHang
 * @date 2018/06/02 23:29
 **/
public class AutoBoxing {

    public static void main(String[] args) {

        int a = new Integer(66);
        Integer b = 18;

        Boolean flag = true;
        boolean isBug = Boolean.FALSE;

    }

}

2.并发库

import java.util.List;
import java.util.Map;
import java.util.Queue;
import java.util.concurrent.*;
import java.util.concurrent.locks.Condition;
import java.util.concurrent.locks.Lock;
import java.util.concurrent.locks.ReentrantLock;

/**
 * 并发库
 *
 * @author biezhi
 * @date 2018/2/8
 */
public class Concurrent {

    /*
        重入锁
     */
    public void lock() {
        Lock lock = new ReentrantLock();
        lock.lock();
        try {
            System.out.println("hello world");
        } finally {
            lock.unlock();
        }
    }

    /*
        线程池
     */
    public void condition() throws InterruptedException {
        Lock      lock      = new ReentrantLock();
        Condition condition = lock.newCondition();
        // do something
        condition.await(10, TimeUnit.SECONDS);
        System.out.println("Get result.");
    }


    public void executorService() {
        ExecutorService executorService = Executors.newFixedThreadPool(3);
        executorService.submit(new Runnable() {
            @Override
            public void run() {
                System.out.println("Task is running.");
            }
        });
    }

    /*
        阻塞队列
     */
    public void blockingDeque() {
        Queue<Integer> blockingDeque = new ArrayBlockingQueue<>(20);
        blockingDeque.add(1);
        blockingDeque.add(2);
        blockingDeque.add(3);

        blockingDeque.peek();
    }

    public void concurrentHashMap() {
        Map<String, Integer> concurrentHashMap = new ConcurrentHashMap<>();
        concurrentHashMap.put("Hello", 1);
        concurrentHashMap.put("World", 2);

        System.out.println(concurrentHashMap.get("Hello"));
    }

    public void copyOnWriteList() {
        List<String> copyOnWriteList = new CopyOnWriteArrayList<>();
        copyOnWriteList.add("a");
        copyOnWriteList.add("b");
        copyOnWriteList.add("c");

        System.out.println(copyOnWriteList.size());
    }

    public void semaphore() {
        Semaphore semaphore = new Semaphore(3);
        try {
            semaphore.acquire();
            System.out.println(Thread.currentThread().getName() + " is working");
            Thread.sleep(1000);
            semaphore.release();
            System.out.println(Thread.currentThread().getName() + " is over");
        } catch (InterruptedException e) {
        }
    }

}

3.枚举

/**
 * 枚举
 *
 * @author GaoHangHang
 * @date 2018/06/12 0:28
 **/
public enum EnumDemo {

    RED, GREEN, YELLOW

}

4.for each

import java.util.Arrays;
import java.util.List;

/**
 * for each
 *
 * @author GaoHangHang
 * @date 2018/06/12 0:30
 **/
public class ForEach {

    public static void main(String[] args) {

        int[] arr = {1, 4, 5, 7};

        for (int i : arr) {
            System.out.println(i);
        }

        List<String> names = Arrays.asList("王爵nice", "Gay冰", "A*熊");
        for (String name : names) {
            System.out.println(name);
        }
    }

}

5.generic

import java.util.HashMap;
import java.util.Map;

/**
 * 泛型
 *
 * 泛型规范数据结构，泛型的本质是参数化类型，所操作的数据被指定为一个参数
 *
 * @author GaoHangHang
 * @date 2018/06/12 0:33
 **/
public class Generic<T> {

    public T getById() {
        return null;
    }

    public static void main(String[] args) {

        Map<String,Integer> map = new HashMap<>();

        Generic<Long> generic = new Generic<>();

    }
}

6.静态导入

import static java.lang.System.out;

/**
 * 静态导入
 *
 * @author GaoHangHang
 * @date 2018/06/12 0:44
 **/
public class StaticImport {

    public static void main(String[] args) {
        out.println("Hi let learn java 8.");
    }

}

7.变长参数

import java.util.Arrays;
import java.util.List;

/**
 * 变长参数
 *
 * @author GaoHangHang
 * @date 2018/06/12 0:53
 **/
public class VarArgs {

    public static List<String> asList(String[] names){
        return Arrays.asList(names);
    }

    public static void main(String[] args) {
        List<String> hello = Arrays.asList("王爵nice", "Gay冰", "A*熊");

    }

}

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