Question

我正在尝试格式化日期以获取特定格式的日期。但它不起作用。不知道为什么！这是我做的：

           for(LeaveApply leaveApply : leaveApplyList) {
                SimpleDateFormat dateFormat = new SimpleDateFormat("dd-MM-yyyy");
                try {
                    leaveApply.setDate(dateFormat.parse(dateFormat.format(leaveApply.getDate())));
                } catch (ParseException e) {
                    e.printStackTrace();
                }
            }

输出结果为：

LeaveApply [id=1, user=id [1]; loginName [admin], leaveType=Medical Leave, leaveTime=Half Leave, date=Fri Apr 15 00:00:00 IST 2011]
LeaveApply [id=0, user=id [1]; loginName [admin], leaveType=Weekend, leaveTime=Full Leave, date=Sat Apr 02 00:00:00 IST 2011]
LeaveApply [id=0, user=id [1]; loginName [admin], leaveType=Weekend, leaveTime=Full Leave, date=Sun Apr 03 00:00:00 IST 2011]
LeaveApply [id=0, user=id [1]; loginName [admin], leaveType=Weekend, leaveTime=Full Leave, date=Sat Apr 09 00:00:00 IST 2011]
LeaveApply [id=0, user=id [1]; loginName [admin], leaveType=Weekend, leaveTime=Full Leave, date=Sun Apr 10 00:00:00 IST 2011]
LeaveApply [id=0, user=id [1]; loginName [admin], leaveType=Weekend, leaveTime=Full Leave, date=Sat Apr 16 00:00:00 IST 2011]
LeaveApply [id=0, user=id [1]; loginName [admin], leaveType=Weekend, leaveTime=Full Leave, date=Sun Apr 17 00:00:00 IST 2011]
LeaveApply [id=0, user=id [1]; loginName [admin], leaveType=Weekend, leaveTime=Full Leave, date=Sat Apr 23 00:00:00 IST 2011]
LeaveApply [id=0, user=id [1]; loginName [admin], leaveType=Weekend, leaveTime=Full Leave, date=Sun Apr 24 00:00:00 IST 2011]
LeaveApply [id=0, user=id [1]; loginName [admin], leaveType=Weekend, leaveTime=Full Leave, date=Sat Apr 30 00:00:00 IST 2011]

如您所见，日期不是所需格式（dd-MM-yyyy）。任何帮助都会很明显。 LeaveApply类是：

public class LeaveApply implements Serializable {

    private static final long serialVersionUID = -7223672229309295181L;
    private long id;
    private User user;
    private String leaveType;
    private String leaveTime;
    private Date date;

    public LeaveApply() {

    }

    public LeaveApply(User user, String leaveType, String leaveTime, Date date) {
        super();
        this.user = user;
        this.leaveType = leaveType;
        this.leaveTime = leaveTime;
        this.date = date;
    }    

    public long getId() {
        return id;
    }

    public void setId(long id) {
        this.id = id;
    }

    public User getUser() {
        return user;
    }

    public void setUser(User user) {
        this.user = user;
    }

    public String getLeaveType() {
        return leaveType;
    }

    public void setLeaveType(String leaveType) {
        this.leaveType = leaveType;
    }

    public String getLeaveTime() {
        return leaveTime;
    }

    public void setLeaveTime(String leaveTime) {
        this.leaveTime = leaveTime;
    }

    public Date getDate() {
        return date;
    }

    public void setDate(Date date) {
        this.date = date;
    }

    @Override
    public String toString() {
        return "LeaveApply [id=" + id + ", user=" + user + ", leaveType=" + leaveType + ", leaveTime=" + leaveTime + ", date=" + date + "]";
    }    
}

我将列表打印为：

for (LeaveApply leaveApply : leaveApplyList) {
        System.out.println(leaveApply);
}

Answer 1

打印时，您需要使用SimpleDateFormat格式化字符串。你的代码现在做的是：

获取时间戳
格式化
将格式化的字符串解析回时间戳
设置时间戳

这是一个相当昂贵的无操作，因为Date对象只包含一个表示时间戳的长整数，没有格式化信息。

此外，在您打印时间戳的位置，您使用默认日期格式。您应该使用此时格式化的日期。

Answer 2

在SimpleDateFormat.format(Date)实施中调用LeaveApply.toString()以获得所需的输出。

Answer 3

在格式化时，您将在String中获得所需的格式，当您解析它时，您将获得Date对象，它将执行toString()，因此您将始终获得默认格式。

格式化日期以获取特定格式的日期

3 个答案: