多线程环境下SimpleDateFormat类安全转换

╰半橙微兮° 2023-07-04 03:23 18阅读 0赞

## 一、SimpleDateFormat类 ##

package state;
    
    import java.text.ParseException;
    import java.text.SimpleDateFormat;
    import java.util.Date;
    
    /**
     * SimpleDateFormat类负责日期的转换与格式化
     *  解决SimpleDateFormat类多线程环境下转换错误问题
     * @author zc
     *
     */
    public class SimpleDateFormatThread  extends Thread{
        private SimpleDateFormat sdf;
        private String dateString;
        
        public SimpleDateFormatThread(SimpleDateFormat sdf,String dateString) {
        	super();
        	this.sdf =sdf;
        	this.dateString =dateString;
        }
        
    	@Override
    	public void run() {
    		
    		try {
    			//System.out.println(dateString);
    			//刚开始日期格式设置错误为YYYY-MM-dd
    			Date date =DateTools.getSimpleDateFormat("yyyy-MM-dd").parse(dateString);
               // System.out.println(date);
    			String newDateString =DateTools.getSimpleDateFormat("yyyy-MM-dd").format(date).toString();
    			
    			if(!newDateString.equals(dateString)) {
    				System.out.println("ThreadName="+this.getName()+"报错日期"+dateString+" 转换日期"+newDateString);
    			}else {
    				System.out.println("ThreadName="+this.getName()+"日期"+dateString+"   转换日期"+newDateString);
    			}
    		} catch (ParseException e) {
    			// TODO Auto-generated catch block
    			e.printStackTrace();
    		}
    		}
    	
    	public static void main(String[] args) {
    		SimpleDateFormat sdf =new SimpleDateFormat("yyyy-MM-dd");
    		String[] dateStringArray =new String[]{
    			"2020-02-05","2020-02-06","2020-02-07","2020-02-08"
    		};
    		SimpleDateFormatThread []threadArray= new SimpleDateFormatThread[4];
    		for(int i=0;i<4;i++) {
    			threadArray[i] =new SimpleDateFormatThread(sdf,dateStringArray[i]);
    		}
    		for(int i=0;i<4;i++) {
    			threadArray[i].start();
    		}
    	}
    }
    
    class DateTools{
    	//ThreadLocal能使线程绑定到指定的对象
    	private static ThreadLocal<SimpleDateFormat> t = new ThreadLocal<SimpleDateFormat>();
    	
    	public static SimpleDateFormat getSimpleDateFormat(String datePattern) {
    		SimpleDateFormat sdf=null;
    		sdf =t.get();
    		if(sdf==null) {
    			
    			sdf =new SimpleDateFormat(datePattern);
    		    t.set(sdf);	
    		}
    		return sdf;
    	}
    }

## 二、线程状态和线程组 ##

### (1)线程5状态 ###

//NEW 尚未启动的线程  
//RUNNABLE Java虚拟机中执行的线程  
//TERMINATED 已经退出的线程  
//BLOCKED 阻塞受监视的线程  
//WAITING 无限等待另一个线程  
//TIMED\_WAITING 等待另一个线程指定时间

package state;
    /**
     *  线程中状态和线程组
     * @author zc
     *
     */
    public class MyThread extends Thread{
       //NEW
       //RUNNABLE
       //TERMINATED
       //BLOCKED
       //WAITING
       //TIMED_WAITING
    	public MyThread() {
    		System.out.println("构造方法中的状态: "+Thread.currentThread().getState());
    	}
    	@Override
    	public void run() {
    		System.out.println("run方法中的状态:"+Thread.currentThread().getState());
    		try {
    			Thread.sleep(1000);
    		} catch (InterruptedException e) {
    			// TODO Auto-generated catch block
    			e.printStackTrace();
    		}
    	}
    	
    	public static void main(String[] args) {
    	    MyThread myThread = new MyThread();
    	    System.out.println("main方法中的状态1 "+ myThread.getState());
    	    
    	    Thread t1 =  new Thread();
    	    Thread t2 =  new Thread();
    	    ThreadGroup group =new ThreadGroup("左氏线程组");
    	    Thread t3 =  new Thread(group,t1);
    	    Thread t4 =  new Thread(group,t2);
    	    t3.start();
    	    t4.start();
    	    System.out.println("活动的线程数量为:  " +group.activeCount());
    	    System.out.println("线程组的名称为:  "+group.getName());
    	    
    	    try {
    			myThread.start();
    			Thread.sleep(1000);
    			System.out.println("main方法中的状态2  "+ myThread.getState());
    		} catch (InterruptedException e) {
    			// TODO Auto-generated catch block
    			e.printStackTrace();
    		}
    	}
    }