Java中的这些骚操作你不能不知道!!!

public void manualClose(String fileName) {
  BufferedReader reader = null;
  try {
      String line;
      reader = new BufferedReader(new FileReader(fileName));
      while ((line = reader.readLine()) != null) {
          ...
      }
  } catch (Exception e) {
      ...
  } finally {
      if (reader != null) {
          try {
              reader.close();
          } catch (IOException e) {
              ...
          }
      }
  }
}

public void autoClose(String fileName) {
  try (BufferedReader reader = new BufferedReader(new FileReader(fileName))) {
      String line;
      while ((line = reader.readLine()) != null) {
          ...
      }
  } catch (Exception e) {
      ...
  }
}

用法：
result = object instanceof class
参数：
Result：布尔类型。
Object：必选项。任意对象表达式。
Class：必选项。任意已定义的对象类。
public interface Monster {
  }
   public static class Dinosaur implements Monster{
  }
   public static void main(String[] args) {
       Dinosaur dinosaur = new Dinosaur();
       System.out.println(dinosaur instanceof Monster);
  }

public void method(int...args);

//方法重载，解决参数个数不确定问题
  public void method(){};
  public void method(int i){};
  public void method(int i, int j){};
  public void method(int i, int j, int k){};
优化之后的形式：
public void method(int i,int ...args);

  public void call(){
      //1、 不使用变参
      method(1);
      //2、 直接调用
      method(1,2,23,4,5,6);
      //3、 数组调用
      int[] arr = {1,2,23,4,5,6};
      method(5,arr);
  }

public static void main(String[] args) {
       for (int i = 0; i < 5; i++) {
           labelA: for (int j = 0; j < 5; j++) {
               for (int k = 0; k < 5; k++) {
                   if (k == 1) {
                       break labelA;
                  }
                   System.out.println(1);
              }
          }
      }
  }

package org.pdool;
import java.util.ArrayList;
import java.util.List;
/**
* 方法引用测试类
* @author 香菜
*/
public class Trytest {
   static List<Player> playerList = new ArrayList<>();
   // 静态方法
   public static void print(String s) {
       System.out.println(s);
  }
   static class Player {
       private String name;
       public Player(String name) {
           this.name = name;
           playerList.add(this);
      }
       private void printName() {
           System.out.println(name);
      }
  }
   public static void main(String[] args) {
       List<String> strList = new ArrayList<>();
       strList.add("香菜");
       strList.add("follow me");
       // 1、静态方法引用
       strList.forEach(Trytest::print);
       // /2、对象方法引用
       strList.forEach(System.out::println);
       // 3、构造函数
       strList.forEach(Player::new);
       // 4、对象方法
       playerList.forEach(Player::printName);
  }
}