Java异常处理机制throws举例详解

package trycatchfinally;

import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.IOException;

/**
 * package:trycatchfinally
 *
 * @Author jimmy-yan
 * @Create 2024/11/19 11:59
 */
public class FinallyTest {

    public static void main(String[] args) {
        FinallyTest f = new FinallyTest();
        f.test1();
    }

    public void test1() {
        try {
            String str = "123";
            str = "abc";
            int i = Integer.parseInt(str);
            System.out.println(i);

        } catch (NumberFormatException e) {
            e.printStackTrace();
            System.out.println(10 / 0);  //在catch中抛出异常
        } finally {
            System.out.println("程序执行结束");
        }
    }


    public void test2() {

        FileInputStream fis = null;
        try {
            File file = new File("D:\\hello.txt");
            fis = new FileInputStream(file);  //可能报FileFonudException

            int data = fis.read(); //可能报IOException
            while (data != -1) {
                System.out.println((char) data);
                data = fis.read(); //可能报IOException
            }

        } catch (FileNotFoundException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        } finally {
            try {
                if (fis != null) {
                    fis.close();  //可能报IOException
                }

            } catch (IOException e) {
                e.printStackTrace();
            }

        }
    }
}

public void test() throws 异常类型1,异常类型2,..{
	//可能存在编译时异常
}

import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.IOException;

/**
 * package:PACKAGE_NAME
 *
 * @Author jimmy-yan
 * @Create 2024/11/19 13:58
 */
public class ThrowsTest {
    public static void main(String[] args) {
        test3();
    }

    public static void test3() {
        try{
            test2();
        }catch (FileNotFoundException e){
            e.printStackTrace();
        }catch (IOException e){
            e.printStackTrace();
        }
    }

    public static void test2() throws FileNotFoundException, IOException {

        File file = new File("D:\\hello.txt");
        FileInputStream fis = new FileInputStream(file);  //可能报FileFonudException

        int data = fis.read(); //可能报IOException
        while (data != -1) {
            System.out.println((char) data);
            data = fis.read(); //可能报IOException
        }
        fis.close();  //可能报IOException
    }
}

/**
 * package:PACKAGE_NAME
 *
 * @Author jimmy-yan
 * @Create 2024/11/19 14:51
 */
public class Throw {
    public static void main(String[] args) {
        Throw t = new Throw();
        t.regist(-9);
        System.out.println(t);
    }

    int id;

    public void regist(int id) {
        if (id > 0) {
            this.id = id;
        } else {
//            System.out.println("输入的非法id");
            //todo 手动抛出异常
            throw new RuntimeException("输入的id非法");
        }
    }

    @Override
    public String toString() {
        return "Throw{" +
                "id=" + id +
                '}';
    }
}