java7 新特性 总结版

Java7语法新特性：

前言，这是大部分的特性，但还有一些没有写进去，比如多核 并行计算的支持加强 fork join 框架；这方面并没有真正写过和了解。也就不写进来了。

Java代码  

    public String generate(String name, String gender) {  
       String title = "";  
       switch (gender) {  
           case "男":  
               title = name + " 先生";  
               break;  
           case "女":  
               title = name + " 女士";  
               break;  
           default:  
               title = name;  
       }  
       return title;  

Java代码  

    public void read(String filename) throws BaseException {  
        FileInputStream input = null;  
        IOException readException = null;  
        try {  
            input = new FileInputStream(filename);  
        } catch (IOException ex) {  
            readException = ex;   //保存原始异常  
        } finally {  
            if (input != null) {  
                try {  
                    input.close();  
                } catch (IOException ex) {  
                    if (readException == null) {  
                        readException = ex;  
                    }  
                }  
            }  
            if (readException != null) {  
                throw new BaseException(readException);  
            }  
        }  
    }  

Java代码  

    public void read(String filename) throws IOException {  
        FileInputStream input = null;  
        IOException readException = null;  
        try {  
            input = new FileInputStream(filename);  
        } catch (IOException ex) {  
            readException = ex;  
        } finally {  
            if (input != null) {  
                try {  
                    input.close();  
                } catch (IOException ex) {  
                    if (readException != null) {    //此处的区别  
                        readException.addSuppressed(ex);  
                    }  
                    else {  
                        readException = ex;  
                    }  
                }  
            }  
            if (readException != null) {  
                throw readException;  
            }  
        }  
    }  

Java代码  

    public void testSequence() {  
        try {  
            Integer.parseInt("Hello");  
        }  
        catch (NumberFormatException | RuntimeException e) {  //使用‘|‘分割，多个类型，一个对象e  
             
        }  
    }  

Java代码  

     public void read(String filename) throws IOException {  
         try (BufferedReader reader = new BufferedReader(new FileReader(filename))) {  
             StringBuilder builder = new StringBuilder();  
    String line = null;  
    while((line=reader.readLine())!=null){  
        builder.append(line);  
        builder.append(String.format("%n"));  
    }  
    return builder.toString();  
         }   
     }  

Java代码  

    public int sum(int... args) {  
        int result = 0;  
        for (int value : args) {  
            result += value;  
        }  
        return result;  
    }  

对collections的支持

Java代码

List<String> list = new ArrayList<String>();       
 list.add("item");       
String item = list.get(0);       
        
 Set<String> set = new HashSet<String>();       
 set.add("item");       
        
 Map<String, Integer> map = new HashMap<String, Integer>();       
 map.put("key", 1);       
 int value = map.get("key");     

 现在你还可以：

    List<String> list = ["item"];       
    String item = list[0];       
           
    Set<String> set = {"item"};       
            
    Map<String, Integer> map = {"key" : 1};       
    int value = map["key"];     

2.自动资源管理

原来:

    BufferedReader br = new BufferedReader(new FileReader(path));       
     try {       
       return br.readLine();       
     } finally {       
        br.close();       
     }      

现在:

    try (BufferedReader br = new BufferedReader(new FileReader(path)) {       
         return br.readLine();       
      }       
             
      //You can declare more than one resource to close:       
             
      try (       
        InputStream in = new FileInputStream(src);       
         OutputStream out = new FileOutputStream(dest))       
     {       
      // code       
     }      

3.对通用实例创建(diamond)的type引用进行了改进

原来:

    Map<String, List<String>> anagrams = new HashMap<String, List<String>>();   

现在:

    Map<String, List<String>> anagrams = new HashMap<>();    

4.数值可加下划线

    int one_million = 1_000_000;    

6.二进制文字

int binary = 0b1001_1001;  

异常catch可以一次处理完而不像以前一层层的surround；

public void newMultiCatch() {  
  
           try {  
  
                 methodThatThrowsThreeExceptions();  
  
           } catch (ExceptionOne | ExceptionTwo | ExceptionThree e) {  
  
                 // log and deal with all Exceptions  
  
           }  
  
     }  

public void newTry() {  
  
  
  
          try (FileOutputStream fos = new FileOutputStream("movies.txt");  
  
                      DataOutputStream dos = new DataOutputStream(fos)) {  
  
                dos.writeUTF("Java 7 Block Buster");  
  
          } catch (IOException e) {  
  
                // log the exception  
  
          }  
  
    }  

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java7 新特性 总结版

原文：http://blog.csdn.net/hjm4702192/article/details/30078877