常用方法歸檔-獲取

                //兩種日期格式
			SimpleDateFormat dateFormat=new SimpleDateFormat("yyyy-MM-dd HH:mm:ss E");
			System.out.println(dateFormat.format(new Date()));
			
			
			SimpleDateFormat dateFormat1=new SimpleDateFormat("yyyy年MM年dd日 HH時:mm分:ss秒 E");
			System.out.println(dateFormat1.format(new Date()));
			
			
		//字符串倒寫
			StringBuffer buffer=new StringBuffer("我愛中國共產黨");
			buffer.reverse();
			System.out.println(buffer);
			
		//獲取當前月最後一天當前日期
			Calendar calendar=Calendar.getInstance();
			calendar.set(Calendar.DAY_OF_MONTH,calendar.getActualMaximum(Calendar.DAY_OF_MONTH));
			Date date=new Date(calendar.getTimeInMillis());
			System.out.println(dateFormat1.format(date));
			
		
			
		//生成隨機數
		Random random=new Random();
		int num=10000;//從<10000中隨機選取10個數
		List list=new ArrayList();
		for (int i = 0; i < 10; i++) {
			list.add(random.nextInt(num));
		}
		Collections.sort(list);//排序輸出
		for (int i = 0; i < list.size(); i++) {
			System.out.println(list.get(i));
		}
		
		
		
		
		//讀寫某磁盤的所有文件
		File file=new File("E:\\學習文檔");
		File [] files=file.listFiles();
		for (int i = 0; i < files.length; i++) {
			if(files[i].isFile()){
				System.out.println(files[i]);
			}
		}
		
		//讀寫某磁盤的所有文件目錄
		for (int i = 0; i < files.length; i++) {
			if(files[i].isDirectory()){
				System.out.println(files[i]);
			}
		}
		
		//判斷某個文件是否存在此文件夾下
		System.out.println(new File("E:\\學習文檔\\記錄卡功能概括.txt").exists());
		
		
		//讀文件
		FileInputStream inputStream = new FileInputStream("E:\\學習文檔\\記錄卡功能概括.txt");
		byte [] bs=new byte[100];
		while (true) {
			int len=inputStream.read(bs);
			if(len<=0)break;
			System.out.println(new String(bs,0,len));
		}
		inputStream.close();
		
		
		//寫文件
		FileWriter fileWriter=new FileWriter("E:\\test.txt");
		fileWriter.write("你好"+System.getProperty("line.separator"));
		fileWriter.write("hello,welcome to BeiJing");
		fileWriter.close();