Java7 新变化

1.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"); 

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：



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

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



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

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



Java代码
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  
} 

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





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

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

becomes:



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

Map<String, List<String>> anagrams = new HashMap<>();4.数值可加下划线



Java代码
int one_million = 1_000_000; 

int one_million = 1_000_000;  

5.在switch中可使用string



Java代码
String s = ...  
switch(s) {  
case "quux":  
    processQuux(s);  
    // fall-through  
 
  case "foo":  
  case "bar":  
    processFooOrBar(s);  
    break;  
 
  case "baz":  
     processBaz(s);  
    // fall-through  
 
  default:  
    processDefault(s);  
    break;  
} 

String s = ...
switch(s) {
case "quux":
    processQuux(s);
    // fall-through

  case "foo":
  case "bar":
    processFooOrBar(s);
    break;

  case "baz":
     processBaz(s);
    // fall-through

  default:
    processDefault(s);
    break;
}
 

6.二进制文字



Java代码
int binary = 0b1001_1001; 

int binary = 0b1001_1001;  

7.简化了可变参数方法的调用



当程序员试图使用一个不可具体化的可变参数并调用一个*varargs* （可变）方法时，编辑器会生成一个“非安全操作”的警告。详情查看





查看原文：http://code.joejag.com/2009/new-language-features-in-java-7/