常用方法归档-获取<日期、字符串倒写、随机数、读写文件>

清疚 2024-04-18 22:39 43阅读 0赞

//两种日期格式
    			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时:mm分:ss秒 E");
    			System.out.println(dateFormat1.format(new Date()));
    			
    			
    		//字符串倒写
    			StringBuffer buffer=new StringBuffer("我爱中国共产党");
    			buffer.reverse();
    			System.out.println(buffer);
    			
    		//获取当前月最后一天当前日期
    			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));
    			
    		
    			
    		//生成随机数
    		Random random=new Random();
    		int num=10000;//从<10000中随机选取10个数
    		List list=new ArrayList();
    		for (int i = 0; i < 10; i++) {
    			list.add(random.nextInt(num));
    		}
    		Collections.sort(list);//排序输出
    		for (int i = 0; i < list.size(); i++) {
    			System.out.println(list.get(i));
    		}
    		
    		
    		
    		
    		//读写某磁盘的所有文件
    		File file=new File("E:\\学习文档");
    		File [] files=file.listFiles();
    		for (int i = 0; i < files.length; i++) {
    			if(files[i].isFile()){
    				System.out.println(files[i]);
    			}
    		}
    		
    		//读写某磁盘的所有文件目录
    		for (int i = 0; i < files.length; i++) {
    			if(files[i].isDirectory()){
    				System.out.println(files[i]);
    			}
    		}
    		
    		//判断某个文件是否存在此文件夹下
    		System.out.println(new File("E:\\学习文档\\记录卡功能概括.txt").exists());
    		
    		
    		//读文件
    		FileInputStream inputStream = new FileInputStream("E:\\学习文档\\记录卡功能概括.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();
    		
    		
    		//写文件
    		FileWriter fileWriter=new FileWriter("E:\\test.txt");
    		fileWriter.write("你好"+System.getProperty("line.separator"));
    		fileWriter.write("hello,welcome to BeiJing");
    		fileWriter.close();