Java8深入学习系列（三）你可能忽略了的新特性

try {
 // 使用流对象
 stream.read();
 stream.write();
} catch(Exception e){
 // 处理异常
} finally {
 // 关闭流资源
 if(stream != null){
 stream.close();
 }
}

public static void tryWithResources() throws IOException {
 try( InputStream ins = new FileInputStream("/home/biezhi/a.txt") ){
 char charStr = (char) ins.read();
 System.out.print(charStr);
 }
}

try ( InputStream is = new FileInputStream("/home/biezhi/a.txt");
 OutputStream os = new FileOutputStream("/home/biezhi/b.txt")
) {
 char charStr = (char) is.read();
 os.write(charStr);
}

try {
 Thread.sleep(20000);
 FileInputStream fis = new FileInputStream("/a/b.txt");
} catch (InterruptedException e) {
 e.printStackTrace();
} catch (IOException e) {
 e.printStackTrace();
}

try {
 Thread.sleep(20000);
 FileInputStream fis = new FileInputStream("/a/b.txt");
} catch (InterruptedException | IOException e) {
 e.printStackTrace();
}

try {
 Class<?> clazz = Class.forName("com.biezhi.apple.User");
 clazz.getMethods()[0].invoke(object);
} catch (IllegalAccessException e) {
 e.printStackTrace();
} catch (InvocationTargetException e) {
 e.printStackTrace();
} catch (ClassNotFoundException e) {
 e.printStackTrace();
}

try {
 Class<?> clazz = Class.forName("com.biezhi.apple.User");
 clazz.getMethods()[0].invoke(object);
} catch (ReflectiveOperationException e){
 e.printStackTrace();
}

BufferedReader br = null;
try {
 new BufferedReader(new FileReader("file.txt"));
 StringBuilder sb = new StringBuilder();
 String line = br.readLine();
 while (line != null) {
 sb.append(line);
 sb.append(System.lineSeparator());
 line = br.readLine();
 }
 String everything = sb.toString();
} catch (Exception e){
 e.printStackTrace();
} finally {
 try {
 br.close();
 } catch (IOException e) {
 e.printStackTrace();
 }
}

Path path2 = Paths.get("/home/biezhi", "a.txt");
Path path3 = Paths.get("/home/biezhi/a.txt");
URI u = URI.create("file:////home/biezhi/a.txt");
Path pathURI = Paths.get(u);

Path filePath = FileSystems.getDefault().getPath("/home/biezhi", "a.txt");

File file = new File("/home/biezhi/a.txt");
Path p1 = file.toPath();
p1.toFile();
file.toURI();

byte[] data = Files.readAllBytes(Paths.get("/home/biezhi/a.txt"));
String content = new String(data, StandardCharsets.UTF_8);

List lines = Files.readAllLines(Paths.get("/home/biezhi/a.txt"));

Files.write(Paths.get("/home/biezhi/b.txt"), "Hello JDK7!".getBytes());

Files.write(Paths.get("/home/biezhi/b.txt"), "Hello JDK7!".getBytes(),
 StandardOpenOption.APPEND);

InputStream ins = Files.newInputStream(path);
OutputStream ops = Files.newOutputStream(path);
Reader reader = Files.newBufferedReader(path);
Writer writer = Files.newBufferedWriter(path);

if (!Files.exists(path)) {
 Files.createFile(path);
 Files.createDirectory(path);
}

Files.createTempFile(dir, prefix, suffix);
Files.createTempFile(prefix, suffix);
Files.createTempDirectory(dir, prefix);
Files.createTempDirectory(prefix);

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

Files.delete(path);

String str = String.join(",", "a", "b", "c");

static  List emptyList();

List persons = Collections.emptyList();

List persons = Collections.emptyList();

@interface Basic {
 String name();
}
@Basic(name="fix")
@Basic(name="todo")
class Person{ }

@interface Basic {
 String name();
}
@interface Basics {
 Basic[] value();
}
@Basics( { @Basic(name="fix") , @Basic(name="todo") } )
class Person{ }

@Repeatable(Basics.class)
@interface Basic {
 String name();
}
@Retention(RetentionPolicy.RUNTIME)
@interface Basics {
 Basic[] value();
}

@Basic(name="fix")
@Basic(name="todo")
class Person{ }

public static void main(String[] args) {
 Basic[] basics = Person.class.getAnnotationsByType(Basic.class);
 Arrays.asList(basics).forEach(a -> {
 System.out.println(a.name());
 });
}

Stream.of("a", "c", null, "d")
 .filter(Objects::nonNull)
 .forEach(System.out::println);

class User {
 String name;
 public String getName() {
 return name;
 }
}
public static String getUserName(User user){
 return user.getName();
}

public static String getUserName(User user){
 if(user != null){
 return user.getName();
 }
 return null;
}

public static String getUserNameByOptional(User user) {
 Optional userName = Optional.ofNullable(user).map(User::getName);
 return userName.orElse(null);
}

Optional emptyUser = Optional.empty();

Optional userOptional = Optional.of(user);

Optional ofNullOptional = Optional.ofNullable(user);

Optional ofNullOptional = Optional.ofNullable(user);
Optional userName = ofNullOptional.map(User::getName);

Object value = map.get("key");

Optional