Java异常处理(2)

异常处理

6. 抛出异常

package cn.zixinyuan;

import cn.webrx.SexException;
import lombok.Data;

/**
 * <p>Project: zixinyuan - OracleUtil
 *
 * @author zixinyuanya [2991228540@qq.com]
 * @version 1.0
 * @since 17
 */
@Data
public class Student1 {
    private int id;
    private String name;
    private String gender;

    public int getId() {
        return id;
    }

    public void setId(int id) {
        this.id = id;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public String getGender() {
        return gender;
    }

    public void setGender(String gender) throws SexException {
        if("男".equals(gender) || "女".equals(gender)) {
        this.gender = gender;
    }else{
            throw new SexException("性别设置异常，必须为男或女");
        }

   this.gender = gender;

       
    }
}

测试

package cn.zixinyuan;

import cn.webrx.SexException;

/**
 * <p>Project: zixinyuan - OracleUtil
 *
 * @author zixinyuanya [2991228540@qq.com]
 * @version 1.0
 * @since 17
 */
public class Test {
    public static void main(String[] args) {
        Student stu = new Student();
        stu.setId(10); stu.setName("jack");
        try {
            stu.setGender("男2");
            int a = 10 / 20;
        } catch (SexException e) {
            System.out.println("性别设置错误。");
        } catch (ArithmeticException e) {
            System.out.println("分母为0了");
        } catch (Exception e) {
            System.out.println("未知exception");
        }
    }
}

7 finally块执行

package cn.zixinyuan;

import cn.webrx.SexException;
import org.jsoup.Jsoup;

import java.io.IOException;

/**
 * <p>Project: zixinyuan - OracleUtil
 *
 * @author zixinyuanya [2991228540@qq.com]
 * @version 1.0
 * @since 17
 */
public class Test1 {
    public static void main(String[] args) {
        Student stu = new Student();
        stu.setId(10); stu.setName("jack");
        try {
            stu.setGender("男");
            Jsoup.connect("https://mi.com").get();
        } catch (SexException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        } catch (IOException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
        show();
    }
    public static void show() {
        try {
            Jsoup.connect("http://www.baidu.com").get();
            System.out.println("try...");
            return;
        } catch (IOException e) {
            System.out.println("catch....");
            return;
        }finally {
            System.out.println("finally....");
        }
    }
        }

8. try-with-resources语句

package cn.zixinyuan;

import java.io.BufferedReader;
import java.io.FileReader;
import java.io.FileWriter;
import java.io.IOException;

/**
 * <p>Project: zixinyuan - OracleUtil
 *
 * @author zixinyuanya [2991228540@qq.com]
 * @version 1.0
 * @since 17
 */
public class Exception {
    public static void main(String[] args) {
        String f = "user.txt";
        try (var fw = new FileWriter(f);

             var fr = new BufferedReader(new FileReader(f))) {
            fw.write("hello world 中文1\r\n");
            fw.flush();
            System.out.println(fr.readLine());
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}

9. finalize()方法

垃圾回收机器（Garbage Collection）,也叫GC，垃圾回收器主要有一下特点：

1. 当对象不再被程序所使用的时候，垃圾回收器将会将其回收

2. 垃圾回收是在后台运行的，我们无法命令垃圾回收器马上回收资源，但是我们可以告诉他可以 尽快回收资源（System.gc()和Runtime.getRuntime().gc()）

3.垃圾回收器在回收某个对象的时候，首先会调用该对象的finalize()方法

4.GC主要针对堆内存

finalize() 是Object里面的一个方法，当一个堆空间中的对象没有被栈空间变量指向的时候，这个对象会等待被java回收： jdk 里面是这样实现的：

protected void finalize() throws Throwable { } 
}

案例测试代码：

public class testFinalize{ 
public static void main(String[] args){ 
Person p = new Person(); 
for(int i = 0 ; i< 1000; i++){ 
p = null;
 }
 System.gc();//增加垃圾回收器启动的概率
      } 
  }
  class Person{ 
  protected void finalize() throws Throwable{ 
  System.out.println("垃圾准备回收中！！！");
     }
 }