Java異常機制---三個關鍵字try catch finally

1. 異常關鍵字---try catch finally 

public abstract class TryCatchFinally {
/**
 * 異常處理方法之一,捕獲異常
 * try  catch  finally
 * try:可能出現異常的邏輯語句，一旦出現異常則停止程序運行,異常被捕獲
 * catch:出現異常,捕獲,拋出異常,需要處理
 * finally:總會被執行,放置關閉資源的代碼,節約內存
 */
	public static void main(String[] args) {
		try {
			Thread.sleep(1000);
		} catch (InterruptedException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}finally {
			System.out.println("finally內的程序總會被執行,用於釋放緩存,節省內存");
		}
	}
}

2. try catch finally return 的執行順序

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

/**
 * try catch finally return 的執行順序
 * {1.執行 try catch 給返回值賦值
 *  2.執行finally
 *  3.返回值}
 *  finally中不能使用return 否則只會返回finally內的返回值，原來的返回值被覆蓋
 * @author Administrator
 *
 */
public class TestException03 {
	public static void main(String[] args) {
		String str = new TestException03().openFile();
		System.out.println(str);
	}
	
	String openFile(){
		System.out.println("aaa");
		try {
			FileInputStream fis = new FileInputStream("E:/new folder/a.txt");
			int a = fis.read();
			System.out.println("bbb");
			return "step1";
		} catch (FileNotFoundException e) {
			// TODO Auto-generated catch block
			System.out.println("catching");
			e.printStackTrace();
			return "step2";
		} catch (IOException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
			return "step3";
		}finally{
			System.out.println("finally");
	//		return "fff";  
		}
	}
}