JDK7 新特性

1. try-with-resources

最初是看OSChina，红薯发文看见的，比较好用。

操作的类只要是实现了AutoCloseable接口就可以在try语句块退出的时候自动调用close方法关闭流资源。

InputStream is = null;
OutputStream os = null;
try {
    // 流
    is = xxx;
    os = xxx;
    //use
    is.read();
    os.write();
} finally {
    // close
    if(stream != null){
        try{
            is.close();
        }catch(Exeception e){
            //xxx
        }
        try{
            os.close();
        }catch(Exeception e){
            //xxx
        }
    }
}

改用新模式

try ( InputStream is  = new FileInputStream("xx");
      OutputStream os = new FileOutputStream("xx")
) {
    //xxx
    //不用关闭了，JVM帮你关闭流
}

 常用于流对象，连接池等的自动关闭。

如果自己的类，实现AutoCloseable，实现其close方法，即可使用。

2. NIO2 文件处理Files

/**
 * This class consists exclusively of static methods that operate on files,
 * directories, or other types of files.
 *
 * 
 In most cases, the methods defined here will delegate to the associated
 * file system provider to perform the file operations.
 *
 * @since 1.7
 */

public final class Files {

读写文件

读取方法

//读取字节
byte[] dataBytes = Files.readAllBytes(Paths.get("D:\\xxx"));
//readline
List lines = Files.readAllLines(Paths.get("D:\\xxx"));

写入方法

示例

//写入文件
Files.write(Paths.get("D:\\xxx"), "xxx".getBytes());
//指定模式写入，比如追加
Files.write(Paths.get("D:\\xxx"), "xxx".getBytes(), StandardOpenOption.APPEND);

/*****************************默认UTF-8编码，可以手工指定***********************************/

构造流模式

InputStream is = Files.newInputStream(path);
OutputStream os = Files.newOutputStream(path);

Reader reader = Files.newBufferedReader(path);
Writer writer = Files.newBufferedWriter(path);

操作目录

//判断存在
Files.exists(path);
//
Files.createFile(path);
//
Files.createDirectory(path);
//文件列表，可以流运算遍历
Stream list(Path dir)
//文件列表
Stream walk(Path start, FileVisitOption... options)

Files.copy(in, path);
Files.move(path, path);
Files.delete(path);


//创建临时文件、临时目录:
Files.createTempFile(dir, prefix, suffix);
Files.createTempFile(prefix, suffix);
Files.createTempDirectory(dir, prefix);
Files.createTempDirectory(prefix);

Path对象

Path path = Paths.get("xxx", "name");
Path path = Paths.get("xxx/name");

Path path = Paths.get(URI.create("xxx路径"));

Path path  = new File("xxx").toPath();
Path path = FileSystems.getDefault().getPath("xxx");

//Path、URI、File之间的转换
File file = new File("xxx");
Path path = file.toPath();
File file = p1.toFile();
URI uri = file.toURI();

3. 多异常统一处理

try {
    //xxx
} catch (AException e) {
    e.printStackTrace();
} catch (BException e) {
    e.printStackTrace();
}

 统一处理如下，粗化异常处理

try {
    //xxx
} catch (AException | BException e) {
    e.printStackTrace();
} 

缺点是异常处理细粒度降低

4. switch(String)

switch可以支持字符串判断条件

switch (""){
    case "":
        break;
                
}

5. 泛型推导

List list = new ArrayList<>();