Exception

import java.io.FileNotFoundException;
import java.io.FileReader;
import java.io.IOException;

public class TestReadFile {
	public static void main(String[] args) {
		FileReader reader=null;
		try{
			reader=new FileReader("d:/a.txt");
			char a=(char)reader.read();
			char a2=(char)reader.read();
			System.out.println(""+a+a2);
		} catch(FileNotFoundException e){
			e.printStackTrace();
		}catch (IOException e) {                      /*不能交换位置，否则会报错Unreachable catch block for FileNotFoundException. It is already 
			handled by the catch block for IOException
				FileNotFoundException 是 IOException的一个子类，子类放前面，父类放后面
			*/
			e.printStackTrace(); 
		}finally{                     //一般在finally里面要关闭资源
			try {
				if(reader!=null){
				reader.close();
				}
			} catch (IOException e) {
				e.printStackTrace();
			}
		}
	}
}

try  catch  finally  return 的执行顺序：

1.执行try ，catch，给定返回值

2.执行finally

3.return

例：

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

public class TestReadFile {
	public static void main(String[] args) {
		String str =new TestReadFile().openFile();
		System.out.println(str);
	}
	String openFile(){
		try {
			System.out.println("aaa");
			FileInputStream fis=new FileInputStream("d:/a.txt");
			int a =fis.read();
			System.out.println("bbb");
			return "step1";
		} catch (FileNotFoundException e) {
			System.out.println("catching!!!!!!");
			e.printStackTrace();
			return "step2";          //先确定返回的值，并不会直接结束运行
		} catch (IOException e) {
			e.printStackTrace();
			return "step 3";
		}finally{
			System.out.println("finally!!!");
			//return "fff";            //不要在finally中使用return
		}
	}
}

运行结果：
aaa
bbb
finally!!!
step1