JDK 7 新特性小结实例代码解析

/***
 * switch支持字符串做参数 jdk7
 * @author huangjiawei
 */
public class SwitchTest {
 public static void switchTest(String arg) {
 switch (arg) {
  case "Lisa":
  System.err.println("我是Lisa!");
  break;
  case "Mike":
  System.err.println("我是Mike！");
  break;
  default:
  System.err.println("我是你的唯一！");
  break;
 }
 }
 public static void main(String[] args) {
 switchTest("Lisa");//我是Lisa!
 switchTest("Mike");//我是Mike！
 switchTest("");//我是你的唯一！
 }
}

/**
 * switch 枚举支持 jdk5
 * @author huangjiawei
 *
 */
public class SwitchMonthTest {
 public static void SwithMonthTest(Month month) {
 switch (month) {
  case JANUARY:
  System.err.println("这是一月份");
  break;
  case FEBRUARY:
  System.err.println("这是二月份");
  break;
  case MARCH:
  System.err.println("这是三月份");
  break;
 }
 }
 public static void main(String[] args) {
 SwithMonthTest(Month.JANUARY);//这是一月份
 SwithMonthTest(Month.FEBRUARY);//这是二月份
 SwithMonthTest(Month.MARCH);//这是三月份 
 }
}

public class BinaryTest {
 private static int a = 16;//十进制
 private static int b = 020;//八进制
 private static int c = 0x10;//十六进制
 private static int d = 0b0001_0000;//二进制，使用分隔符隔开
 public static void main(String[] args) {
 System.err.println(a);//16
 System.err.println(b);//16
 System.err.println(c);//16
 System.err.println(d);//16
 }
}

import java.io.BufferedReader;
import java.io.FileReader;
public class TryTest {
 
 /*
 * 接受一个文件的路径 Java 7之前
 */
 public static String tryTest(String path) {
 
 BufferedReader br = null; 
 try { 
   br = new BufferedReader(new FileReader(path));
   return br.readLine();
 } catch (Exception e) {
   System.err.println("BufferedReader Exception" + e);
 } finally {
   if (br != null) {
     try {
       br.close();
       br.ready();//流已经关闭，此处抛出异常
     } catch (Exception e) {
       System.err.println("BufferedReader close Exception" + e);
     }
   }
 }
 return "";
 }
 
 /*
 * 接受一个文件的路径 Java7
 */
 public static String tryTest1(String path) {
 /*
  * 当try语句块运行结束时，FileInputStream 会被自动关闭。这是因为FileInputStream 实现了java中的java.lang.AutoCloseable接口。
  * 所有实现了这个接口的类都可以在try-with-resources结构中使用。
  */
 try (BufferedReader br = new BufferedReader(new FileReader(path))) { 
   return br.readLine();
 } catch (Exception e) {
   System.err.println("BufferedReader Exception" + e);
 }
 return "";
 }
 
 public static void main(String[] args) {
 tryTest("C:\\Users\\huangjiawei\\Desktop\\my-release-key.keystore");
 tryTest1("C:\\Users\\huangjiawei\\Desktop\\my-release-key.keystore");
 }
}

import java.util.Date;
/**
 * 多个catch语句永远只执行第一个匹配到的catch异常，后面有再多的catch都会被忽略掉
 * @author huangjiawei
 *
 */
public class CatchTest {
 /*
 * java 7以前
 */
 public static void CatchTest() {
 int a = 100;
 int b = 0;
 Date date = null;
 try {
  System.err.println(date.getTime());//这里抛出异常，下面的语句就不会执行啦！
  int result = a/b;//不会执行
  System.err.println(result);//不会执行
 }catch(NullPointerException e) {
  System.err.println(e);//java.lang.NullPointerException
 }catch(ArithmeticException e){
  System.err.println(e);
 }catch (Exception e) {
  System.err.println(e);
 }
 }
 /*
 * java 7
 */
 public static void CatchTest1() {
 int a = 100;
 int b = 0;
 Date date = null;
 try {
  int result = a/b;
  System.err.println(result);
  System.err.println(date.getTime());
 }catch(ArithmeticException | NullPointerException e) {
  System.err.println(e);//java.lang.ArithmeticException: / by zero
 }
 }
 
 public static void main(String[] args) {
 CatchTest();
 CatchTest1();
 }
}

import java.util.ArrayList;
import java.util.List;
public class TypeTest {
 
 /*
 * java 7前，前后<>都必须声明类型
 */
 List<String> list = new ArrayList<String>();
 
 /*
 * java 7，后<>不须声明类型,自动根据前面<>推断其类型
 */
 List<String> list1 = new ArrayList<>();
}

import java.nio.file.Path;
import java.nio.file.Paths;
public class PathPathsTest {
 public static void main(String[] args) {
 Path path = Paths.get("C:\\\\Users\\\\huangjiawei\\\\Desktop\\\\my-release-key.keystore");
 System.out.println("文件节点数:" + path.getNameCount()); //文件节点数:4
 System.out.println("文件名称:" + path.getFileName()); //文件名称:my-release-key.keystore
 System.out.println("文件根目录:" + path.getRoot()); //文件根目录:C:\
 System.out.println("文件上级关联目录:" + path.getParent());//文件上级关联目录:C:\Users\huangjiawei\Desktop
 }
}

Files.copy(Paths.get("/test/src.xml"), Paths.get("/test/target.xml"));

import java.nio.file.FileSystems;
import java.nio.file.Path;
import java.nio.file.Paths;
import java.nio.file.StandardWatchEventKinds;
import java.nio.file.WatchEvent;
import java.nio.file.WatchKey;
import java.nio.file.WatchService;
/**
 * 文件监控系统
 * @author huangjiawei
 */
public class WatchViewTest {
 public static void testWatch() { 
   /* 监控目标路径 */
   Path path = Paths.get("C:\\Users\\huangjiawei\\Desktop");
   try {
     /* 创建文件监控对象. */
     WatchService watchService = FileSystems.getDefault().newWatchService();
     /* 注册文件监控的所有事件类型. */
     path.register(watchService, StandardWatchEventKinds.ENTRY_CREATE, StandardWatchEventKinds.ENTRY_DELETE,
         StandardWatchEventKinds.ENTRY_MODIFY);
     /* 循环监测文件. */
     while (true) {
       WatchKey watchKey = watchService.take();
       /* 迭代触发事件的所有文件 */
       for (WatchEvent<?> event : watchKey.pollEvents()) {
         System.out.println(event.context().toString() + " 事件类型：" + event.kind());
       }
       if (!watchKey.reset()) {
         return;
       }
     }
   } catch (Exception e) {
     e.printStackTrace();
   }
 }
 public static void main(String[] args) {
 testWatch();
 }
}