java异常处理的使用。

package com.robert.test1;

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

/**
 * @author Administrator
 *测试try catch块的执行路径
 */
public class TryCatchTest {

	public static void main(String[] args) {
		
		try 
		{
			InputStream inputStream = new FileInputStream("abc");
			inputStream.read();
		} 
		catch (FileNotFoundException e) 
		{
			System.out.println("throw a FileNotFoundException");
		} 
		catch (IOException e) 
		{
			System.out.println("throw a IOException!");
		}
		System.out.println("hello world!");
	}
}


当文件找不到时：

输出：

throw a FileNotFoundException
hello world!

package com.robert.test1;

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

/**
 * @author Administrator
 *测试try catch块的执行路径
 */
public class TryCatchTest {

	public static void main(String[] args) {
		
		try {
			InputStream inputStream = new FileInputStream("abc");
			inputStream.read();
		} catch (FileNotFoundException e) {
			System.out.println("throw a FileNotFoundException");
			return;
		} catch (IOException e) {
			System.out.println("throw a IOException!");
			return;
		}
		System.out.println("hello world!");
	}
}

在catch块中加入return ,当程序遇到异常（FileNotFoundException,IOException）的时候会被返回。即catch后的代码不会被执行。

输出：

throw a FileNotFoundException

package com.robert.test1;

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

/**
 * @author Administrator
 *测试try catch块的执行路径
 */
public class TryCatchTest {

	public static void main(String[] args) {
		
		try 
		{
			InputStream inputStream = new FileInputStream("abc");
			inputStream.read();
		} 
		catch (FileNotFoundException e) 
		{
			System.out.println("throw a FileNotFoundException");
			return;
		} 
		catch (IOException e) 
		{
			System.out.println("throw a IOException!");
			return;
		}
		finally
		{
			System.out.println("finally");
		}
		System.out.println("hello world!");
	}
}

如果后finally,程序遇到异常（FileNotFoundException,IOException） ,finally块中的代码也会被执行到。

输出：

throw a FileNotFoundException
finally