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 + " "); } 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); } }); }