Java新特性
2017-04-24 本文已影响19人
嘉美伯爵
Java5新特性
可变参数
package practice;
public class change {
public static void main(String []args){
System.out.println(add(new int[] {1,2,3}));
System.out.println(add(new int[] {10,30}));
}
public static int add(int data[]){ //接收
int num = 0;
for(int x=0;x<data.length;x++){
num += data[x];
}
return num;
}
}
package practice;
public class change {
public static void main(String []args){
System.out.println(add(new int[] {1,2,3}));
System.out.println(add(new int[] {10,30}));
}
public static int add(int ... data){ //接收
int num = 0;
for(int x=0;x<data.length;x++){
num += data[x];
}
return num;
}
}
//运行结果一致，可以接收数组。
foreach循环
package practice;
public class change {
public static void main(String []args){
int data[] = new int [] {1,2,3,4,5};
for(int x : data){
System.out.println(x);
}
}
}
静态导入
引入：
package cn.fovegage.util;
public class MyMath {
public static int add(int x,int y){
return x+y;
}
public static int div(int x,int y){
return x/y;
}
}
-----------------------------------------------
package cn.fovegage.practice;
import cn.fovegage.util.MyMath;
public class Demo {
public static void main(String []args){
System.out.println("加法操作："+MyMath.add(10,20));
System.out.println("加法操作："+MyMath.div(10,2));
}
}
静态导入：
package cn.fovegage.util;
public class MyMath {
public static int add(int x,int y){
return x+y;
}
public static int div(int x,int y){
return x/y;
}
}
-----------------------------------------------
package cn.fovegage.practice;
import static cn.fovegage.util.MyMath.*;
public class Demo {
public static void main(String []args){
System.out.println("加法操作："+add(10,20));
System.out.println("加法操作："+div(10,2));
}
}
Java8新特性
接口定义的增强（可以在父类用static或default定义普通类）
default定义普通类
package cn.fovegage.Demo;
interface IMessage{
public void print();
default void fun(){
System.out.print("default操作！");
}
}
class MessageImpl implements IMessage{
public void print(){
System.out.println("Hello World!!!");
}
}
public class JouKou {
public static void main(String[] args) {
// TODO Auto-generated method stub
IMessage i = new MessageImpl();
i.fun();
}
}
static定义的操作(static定义的方法可以直接用类调用)
package cn.fovegage.Demo;
interface IMessage{
public void print();
default void fun(){
System.out.println("default操作！");
}
static void funa(){
System.out.println("static操作！");
}
}
class MessageImpl implements IMessage{
public void print(){
System.out.println("Hello World!!!");
}
}
public class JouKou {
public static void main(String[] args) {
// TODO Auto-generated method stub
IMessage i = new MessageImpl();
i.fun();
IMessage.funa();
}
}
Lamda表达式
匿名内部类(简化代码)
package cn.fovegage.Demo;
interface IMessagea{
public void print();
}
public class Lamda {
public static void main(String[] args) {
// TODO Auto-generated method stub
fun(new IMessagea(){
public void print(){
System.out.println("Heelo World!!!");
}
});
}
public static void fun(IMessagea im){
im.print();
}
}
Lamda表达式
三种表达形式
package cn.fovegage.Demo;
interface IMessagea{
public void print();
}
public class Lamda {
public static void main(String[] args) {
// TODO Auto-generated method stub
fun(() -> System.out.println("Heelo World!!!"));
}
public static void fun(IMessagea im){
im.print();
}
}
有参单行输出
package cn.fovegage.Demo;
interface IMessagea{
public void print(String str);
}
public class Lamda {
public static void main(String[] args) {
// TODO Auto-generated method stub
fun((s) -> System.out.println(s));
}
public static void fun(IMessagea im){
im.print("Hello World!!!");
}
}
多行语句
package cn.fovegage.Demo;
interface IMessagea{
public void print(String str);
}
public class Lamda {
public static void main(String[] args) {
// TODO Auto-generated method stub
fun((s) -> {
s = s.toUpperCase();
System.out.println(s);
});
}
public static void fun(IMessagea im){
im.print("Hello World!!!");
}
}
表达式
package cn.fovegage.Demo;
interface IMessagea{
public int add(int x,int y);
}
public class Lamda {
public static void main(String[] args) {
// TODO Auto-generated method stub
fun((s1,s2) -> s1+s2);
}
public static void fun(IMessagea im){
System.out.print(im.add(10, 20));
}
}
方法引用(函数式接口（）在接口中使用，且接口中只可定义一个方法)
引用静态方法
package cn.fovegage.Demo;
interface IMessage<P,R>{ //P是引用方法的参数类型，R是引用方法的返回类型
public R zhuanhuan(P p);
}
public class yinyong {
public static void main(String[] args) {
// TODO Auto-generated method stub
//将String.VauleOf()的方法转换成IMessageq的接口的zhuanhuan()方法
IMessage<Integer,String> msg = String :: valueOf;
String str = msg.zhuanhuan(1000);
System.out.println(str.replaceAll("0", "9"));
}
}
普通方法引用
package gg;
@FunctionalInterface
interface IMessage<R>{
public R upper();
}
public class f {
public static void main(String[] args) {
// TODO Auto-generated method stub
IMessage<String> msg = "hello" :: toUpperCase;
String str = msg.upper();
System.out.print(str);
}
}
特殊方法的引用
package gg;
@FunctionalInterface
interface IMessage<P>{
public int upper(P p1,P p2);
}
public class f {
public static void main(String[] args) {
// TODO Auto-generated method stub
IMessage<String> msg = String :: compareTo;
System.out.print(msg.upper("A", "B"));
}
}
引用构造方法（一般构造方法只有在实例化的时候才能引用，静态方法则可以直接引用）
package gg;
@FunctionalInterface
interface IMessage<P>{
public P upper(String name,double price);
}
class Book{
private String name;
private double price;
public Book(String name,double price){
this.name = name;
this.price = price;
}
@Override
public String toString() {
// TODO Auto-generated method stub
return "书名："+this.name+" "+"价格："+this.price;
}
}
public class f {
public static void main(String[] args) {
// TODO Auto-generated method stub
IMessage<Book> msg = Book :: new;
Book book = msg.upper("Java", 36.6);
System.out.print(book);
}
}
