java基础---->java的新特性（一）

　　通过简单的实例来感觉一下java7和java8的新特性。当那条唯捷径省略了朝拜者，我便在一滴花露中瞬间彻悟。

java7代码实例

一、java7中switch中可以字符串

@Test
public void jdk7Switch() {
String name = "huhx";
switch (name) {
case "huhx":
System.out.println("name is = " + name);
break;
case "linux":
System.out.println("name is = " + name);
break;
default:
System.out.println("my name is huhx.");
}
}

二、二进制和数字下划线的分割的支持

@Test
public void jdk7Binary() {
int bNum = 0b11110001;
System.out.println(bNum); // 241
int num = 12_234_34_45;
System.out.println(num); // 122343445
}

三、关于异常和自动的资源管理

@Test
public void jdk7CatchExceptions() {
try {
Integer.parseInt("aa");
} catch (NumberFormatException | MaxRunTimeException e) {
e.printStackTrace();
}
}

@Test
public void jdk7TryWithResource() throws IOException {
try (BufferedReader reader = new BufferedReader(new FileReader("C:/Users/76801/Desktop/huhx.txt"))) {
StringBuilder builder = new StringBuilder();
String line = null;
while ((line = reader.readLine()) != null) {
builder.append(line + "\n");
}
System.out.println(builder.toString());
}
}

java8代码实例

一、Lambda的简单使用

package com.tomhu.huhx.java8;

import org.junit.Test;

import java.util.function.Function;

/**
* @Author: huhx
* @Date: 2017-09-21 上午 9:10
*/
public class LambdaTest {

@Test
public void lambdaThread1() {
Thread thread = new Thread(() -> {
System.out.println("hello wolrd");
});
thread.start();
}

@Test
public void lambaFunction1() {
// Function是1.8里面的函数式接口
Function<Integer, String> function1 = new Function<Integer, String>() {
@Override
public String apply(Integer integer) {
return null;
}
};

// lambda expression
Function<Integer, String> function2 = (t) -> String.valueOf(t);

// 引用的方式
Function<Integer, String> function3 = String::valueOf;
}
}

二、函数式接口

定义一个函数式接口：DefaultFunInterface]

package com.tomhu.huhx.java8;

/**
* @Author: huhx
* @Date: 2017-09-21 上午 9:35
*/
public interface DefaultFunInterface {
default int count() {
return 1;
}

public static int find() {
return 1;
}
}

对上述的接口测试：InterfaceSuper

package com.tomhu.huhx.java8;

import org.junit.Test;

/**
* @Author: huhx
* @Date: 2017-09-21 上午 9:34
*/
public class InterfaceSuper {
@Test
public void defaultMethond() {
DefaultFunInterface funInterface = new SubDefaultFunClass();
System.out.println(funInterface.count()); // 1
}

// 接口可以直接调用自己的static方法
@Test
public void staticMethod() {
System.out.println(DefaultFunInterface.find()); // 1
}
}

class SubDefaultFunClass implements DefaultFunInterface {
@Override
public int count() {
return 0;
}
}

三、java中nio的改进

package com.tomhu.huhx.java8;

import org.junit.Test;

import java.io.File;
import java.io.IOException;
import java.nio.file.Files;
import java.time.LocalDate;
import java.util.ArrayList;
import java.util.List;

/**
* @Author: huhx
* @Date: 2017-09-21 上午 9:39
*/
public class StreamTest {
@Test
public void streamTest1() {
List<String> stringList = new ArrayList<>();
stringList.add("linux");
stringList.add("liuling");
stringList.add("liuli");
stringList.add("tomhu");
stringList.add("zhoucf");
stringList.stream().filter((s -> s.startsWith("l"))).forEach(System.out::print); // linuxliulingliuli
}

@Test
public void findAllFiles() throws IOException {
Files.list(new File(".").toPath()).forEach(System.out::println);
}

@Test
public void localDateTest() {
LocalDate localDate = LocalDate.now(); // 2017-09-21
System.out.println(localDate);
localDate = LocalDate.ofYearDay(2017, 333); // 2017-11-29
System.out.println(localDate);
}
}

四、更加简单的遍历Collection类型

public void listForEachTest() {
List<String> lists = Arrays.asList("huhx", "linux", "liuling");
lists.forEach(item -> {
if (item.startsWith("l")) {
System.out.println(item);
}
});
lists.forEach(System.out::println);

lists.stream().filter(item -> item.contains("l")).forEach(System.out::println);
}

public void mapForEachTest() {
Map<String, String> map = new HashMap<>();
map.put("name", "huhx");
map.put("pass", "1234");

map.forEach((key, val)-> {
if (key.equals("name")) {
System.out.println(val);
}
});
}

友情链接

比较详细的java8介绍：https://www.ibm.com/developerworks/cn/java/j-lo-jdk8newfeature/index.html

详细的java8介绍：http://www.importnew.com/11908.html