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