Java 比较两个日期的方法

Java 比较两个日期的方法

 

Java的日期类型比较可以使用如下三种方法：

1. 使用Date类的CompareTo方法
2. 使用Date类的equals(), before() 和after()方法
3. 使用Calendar类的equals(),before()和after()方法

【Java代码】

import java.text.DateFormat;
import java.text.ParseException;
import java.text.SimpleDateFormat;
import java.util.Calendar;
import java.util.Date;

public class HashtableDemo {

    public static void main(String args[]) throws AssertionError, ParseException {

        DateFormat df = new SimpleDateFormat("dd-MM-yyyy");

        //comparing date using compareTo method in Java
        System.out.println("Comparing two Date in Java using CompareTo method");
        compareDatesByCompareTo(df, df.parse("01-01-2012"), df.parse("01-01-2012"));
        compareDatesByCompareTo(df, df.parse("02-03-2012"), df.parse("04-05-2012"));
        compareDatesByCompareTo(df, df.parse("02-03-2012"), df.parse("01-02-2012"));

        //comparing dates in java using Date.before, Date.after and Date.equals
        System.out.println("Comparing two Date in Java using Date's before, after and equals method");
        compareDatesByDateMethods(df, df.parse("01-01-2012"), df.parse("01-01-2012"));
        compareDatesByDateMethods(df, df.parse("02-03-2012"), df.parse("04-05-2012"));
        compareDatesByDateMethods(df, df.parse("02-03-2012"), df.parse("01-02-2012"));

        //comparing dates in java using Calendar.before(), Calendar.after and Calendar.equals()
        System.out.println("Comparing two Date in Java using Calendar's before, after and equals method");
        compareDatesByCalendarMethods(df, df.parse("01-01-2012"), df.parse("01-01-2012"));
        compareDatesByCalendarMethods(df, df.parse("02-03-2012"), df.parse("04-05-2012"));
        compareDatesByCalendarMethods(df, df.parse("02-03-2012"), df.parse("01-02-2012"));

    }

    public static void compareDatesByCompareTo(DateFormat df, Date oldDate, Date newDate) {
        //how to check if date1 is equal to date2
        if (oldDate.compareTo(newDate) == 0) {
            System.out.println(df.format(oldDate) + " and " + df.format(newDate) + " are equal to each other");
        }

        //checking if date1 is less than date 2
        if (oldDate.compareTo(newDate) < 0) {
            System.out.println(df.format(oldDate) + " is less than " + df.format(newDate));
        }

        //how to check if date1 is greater than date2 in java
        if (oldDate.compareTo(newDate) > 0) {
            System.out.println(df.format(oldDate) + " is greater than " + df.format(newDate));
        }
    }

    public static void compareDatesByDateMethods(DateFormat df, Date oldDate, Date newDate) {
        //how to check if two dates are equals in java
        if (oldDate.equals(newDate)) {
            System.out.println(df.format(oldDate) + " and " + df.format(newDate) + " are equal to each other");
        }

        //checking if date1 comes before date2
        if (oldDate.before(newDate)) {
            System.out.println(df.format(oldDate) + " comes before " + df.format(newDate));
        }

        //checking if date1 comes after date2
        if (oldDate.after(newDate)) {
            System.out.println(df.format(oldDate) + " comes after " + df.format(newDate));
        }
    }

    public static void compareDatesByCalendarMethods(DateFormat df, Date oldDate, Date newDate) {

        //creating calendar instances for date comparision
        Calendar oldCal = Calendar.getInstance();
        Calendar newCal = Calendar.getInstance();

        oldCal.setTime(oldDate);
        newCal.setTime(newDate);

        //how to check if two dates are equals in java using Calendar
        if (oldCal.equals(newCal)) {
            System.out.println(df.format(oldDate) + " and " + df.format(newDate) + " are equal to each other");
        }

        //how to check if one date comes before another using Calendar
        if (oldCal.before(newCal)) {
            System.out.println(df.format(oldDate) + " comes before " + df.format(newDate));
        }

        //how to check if one date comes after another using Calendar
        if (oldCal.after(newCal)) {
            System.out.println(df.format(oldDate) + " comes after " + df.format(newDate));
        }
    }
}

运行结果