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

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();
		}
	}
}

 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();
		
	}
}