java声明方法抛出的异常

雨点打透心脏的1/2处 2022-04-06 09:17 257阅读 0赞

# java声明方法抛出的异常 #

TestExceptions.java

import java.io.*;
    
    //异常
    public class TestExceptions {
    	public static void main(String[] args) {
    		
    	}
    	
    	void f() {//throws FileNotFoundException , IOException 
    		FileInputStream in = new FileInputStream("myfile.txt");
    		int b;
    		b = in.read();
    		while (b != -1) {
    			System.out.print((char) b);
    			b = in.read();
    		}
    	}
    }

抛出异常

F:\java>javac TestExceptions.java
    TestExceptions.java:10: 错误: 未报告的异常错误FileNotFoundException; 必须对其进行捕获或声明以便抛出
                    FileInputStream in = new FileInputStream("myfile.txt");
                                         ^
    TestExceptions.java:12: 错误: 未报告的异常错误IOException; 必须对其进行捕获或声明以便抛出
                    b = in.read();
                               ^
    TestExceptions.java:15: 错误: 未报告的异常错误IOException; 必须对其进行捕获或声明以便抛出
                            b = in.read();
                                       ^
    3 个错误
    
    F:\java>

给方法抛出异常

编译没有报异常

F:\java>javac TestExceptions.java
    
    F:\java>

import java.io.*;
    
    //异常
    public class TestExceptions {
    	public static void main(String[] args) {
    		
    	}
    	
    	//throwsthrows FileNotFoundException , IOException
    	void f() throws FileNotFoundException , IOException {
    		FileInputStream in = new FileInputStream("myfile.txt");
    		int b;
    		b = in.read();
    		while (b != -1) {
    			System.out.print((char) b);
    			b = in.read();
    		}
    	}
    	//throws IOException
    	void f2() throws IOException {
    		
                    //捕捉f()方法中可能出现的异常
    		try {
    			f();
    		} catch (FileNotFoundException e) {
    			System.out.println(e.getMessage());
    		} catch (IOException e) {
    			e.printStackTrace();
    		}
    		
    	}
    }

import java.io.*;
    
    //异常
    public class TestExceptions {
    	public static void main(String[] args) /*throws Exception*/ {
    		try {
    			TestExceptions te = new TestExceptions();
    			te.f2();
    		} catch(IOException e) {
    			e.printStackTrace();
    			
    		}
    		
    	}
    	
    	//throwsthrows FileNotFoundException , IOException
    	void f() throws FileNotFoundException , IOException {
    		FileInputStream in = new FileInputStream("myfile.txt");
    		int b;
    		b = in.read();
    		while (b != -1) {
    			System.out.print((char) b);
    			b = in.read();
    		}
    	}
    	
    	void f2() throws IOException {
    		/*
    		方法一：
    		//捕捉f()方法中可能出现的异常
    		try {
    			f();
    		} catch (FileNotFoundException e) {
    			System.out.println(e.getMessage());
    		} catch (IOException e) {
    			e.printStackTrace();
    		}
    		*/
    		
    		/*
    			方法二：
    			在f2() 方法后抛出异常f2() throws IOException
    		*/
    		f();
    		
    	}
    }