Java8-Lambda

前言:学习一下java8新的Lambda表达式

Lambda 语法

// 1. 不需要参数,返回值为 5
() -> 5

// 2. 接收一个参数(数字类型),返回其2倍的值
x -> 2 * x

// 3. 接受2个参数(数字),并返回他们的差值
(x, y) -> x – y

// 4. 接收2个int型整数,返回他们的和
(int x, int y) -> x + y

// 5. 接受一个 string 对象,并在控制台打印,不返回任何值(看起来像是返回void)
(String s) -> System.out.print(s)

实例1

List

/**
 * @author shency
 * @description: lambda
 */
public class Test{
    public static void main(String[] args) {
        List<String> currencyList = Arrays.asList("CNY","USD","AUD","EUR","GBP","HKD","JPY","NZD","HKD","SGD");
        System.out.println("Java8 lambda:");
        currencyList.forEach(x -> System.out.println(x));

        System.out.println("Java8 方法引用");
        currencyList.forEach(System.out::println);
    }
}

线程

/**
 * @author shency
 * @description: lambda
 */
public class Test{
    public static void main(String[] args) {
        new Thread( () -> System.out.println("Java8 lambda") ).start();
    }
}

实例2

实体类

/**
 * @author shency
 * @description: Money
 */
public class Money {
    // 金额
    private double amount;
    // 币种
    private String currency;
    public Money(){};
    public Money(double amount,String currency){
        this.amount = amount;
        this.currency = currency;
    }

    public double getAmount() {
        return amount;
    }

    public void setAmount(double amount) {
        this.amount = amount;
    }

    public String getCurrency() {
        return currency;
    }

    public void setCurrency(String currency) {
        this.currency = currency;
    }
}

Test

import java.util.*;

/**
 * @author shency
 * @description: lambda
 */
public class Test {
    public static void main(String[] args) {
        Map<String,String> currencyMap = new HashMap<String,String>();
        currencyMap.put("CNY","¥");
        currencyMap.put("USD","$");
        currencyMap.put("AUD","$");
        currencyMap.put("EUR","€");
        currencyMap.put("GBP","￡");
        List<Money> moneyList = new ArrayList<Money>();
        moneyList.add(new Money(15090, "CNY"));
        moneyList.add(new Money(33200, "USD"));
        moneyList.add(new Money(46500, "AUD"));
        moneyList.add(new Money(76320, "EUR"));
        moneyList.add(new Money(26760, "GBP"));

        List<String> list = new ArrayList<String>();
        moneyList.forEach(money -> {
            list.add(money.getAmount() + currencyMap.get(money.getCurrency()));
        });
        list.forEach(s ->{
            System.out.println(s);
        });
    }
}