Java 7 的 新特性代码实例

1. switch 中使用字符串变量

public void testStringSwitch(String direction) {
  switch (direction) {
     case "up":
	 y--;
     break;

     case "down":
	 y++;
     break;

     case "left":
	 x--;
     break;

     case "right":
	 x++;
     break;

    default:
	System.out.println("Invalid direction!");
    break;
  }
}

 

public void testStringSwitch(String direction) {
  switch (direction) {
     case "up":
	 y--;
     break;

     case "down":
	 y++;
     break;

     case "left":
	 x--;
     break;

     case "right":
	 x++;
     break;

    default:
	System.out.println("Invalid direction!");
    break;
  }
}

 

 2. 简化泛型对象创建

 

// Java 7 以前版本
Map<String,Map<String,int>>m=new HashMap<String, Map<String,int>>();

// Java 7
Map<String, Map<String, int>> m = new HashMap<>();

 3. 多异常处理

 

try {
    Class a = Class.forName("wrongClassName");
    Object instance = a.newInstance();
} catch (ClassNotFoundException | IllegalAccessException |
   InstantiationException ex) {
   System.out.println("Failed to create instance");
}

 4. 资源的自动释放

 

try (BufferedReader in=new BufferedReader(new FileReader("test.txt")))
{
    String line = null;
    while ((line = in.readLine()) != null) {
	System.out.println(line);
    }
} catch (IOException ex) {
    ex.printStackTrace();
}

 5. 文件 IO API 的改进 下面是列出一个文件中所有行并打印的方法

 

List<String> lines =  Files.readAllLines(
FileSystems.getDefault().getPath("test.txt"), StandardCharsets.UTF_8);

for (String line : lines) System.out.println(line);

 6. 通过 invokedynamic支持非 Java 语言(详情)

 7. JLayerPane (详情)