java list lamada 数量前三

最初设想使用：时间long型

private void testTimes() throws InterruptedException{
Calendar cal=Calendar.getInstance();
cal.add(Calendar.DATE, 1);
cal.set(cal.get(Calendar.YEAR), cal.get(Calendar.MONTH), cal.get(Calendar.DAY_OF_MONTH), 0, 0, 0);
Long time1=cal.getTimeInMillis();
Calendar ca2=Calendar.getInstance();
ca2.add(Calendar.DATE, 1);
ca2.set(cal.get(Calendar.YEAR), cal.get(Calendar.MONTH), cal.get(Calendar.DAY_OF_MONTH), 0, 0, 0);
Long time2=ca2.getTimeInMillis();
System.out.println(time1+"--"+time2);
}

发现整型可能不一致，即有时候一致，有时候不一致。

经测算发现，Collections提供了排序功能：

private void testSort(){
List cals=new ArrayList();
Calendar cal3=Calendar.getInstance();
cal3.add(Calendar.DATE, 2);
cal3.set(cal3.get(Calendar.YEAR), cal3.get(Calendar.MONTH), cal3.get(Calendar.DAY_OF_MONTH), 0, 0, 0);
Calendar cal4=Calendar.getInstance();
cal4.add(Calendar.DATE, 2);
cal4.set(cal4.get(Calendar.YEAR), cal4.get(Calendar.MONTH), cal4.get(Calendar.DAY_OF_MONTH), 0, 0, 0);
Calendar cal1=Calendar.getInstance();
cal1.add(Calendar.DATE, 2);
cal1.set(cal1.get(Calendar.YEAR), cal1.get(Calendar.MONTH), cal1.get(Calendar.DAY_OF_MONTH), 0, 0, 2);
Calendar cal2=Calendar.getInstance();
cal2.add(Calendar.DATE, 2);
cal2.set(cal2.get(Calendar.YEAR), cal2.get(Calendar.MONTH), cal2.get(Calendar.DAY_OF_MONTH), 0, 0, 0);
cals.add(cal3);
cals.add(cal4);
cals.add(cal1);
cals.add(cal2);
Calendar minTime=Collections.min(cals);
System.out.println(DateUtils.formatDate(Collections.min(cals).getTime(),"yyyy-MM-dd HH:mm:ss"));
for(int i=0;i
if(DateUtils.defaultFormatDate(minTime.getTime()).equals(DateUtils.defaultFormatDate(cals.get(i).getTime()))){
System.out.println(DateUtils.formatDate(cals.get(i).getTime(),"yyyy-MM-dd HH:mm:ss"));
}
}
/* for(int i=0;i
System.out.println(DateUtils.formatDate(cals.get(i).getTime(),"yyyy-MM-dd HH:mm:ss"));
}
Collections.sort(cals);
//排序后
for(int i=0;i
System.out.println(DateUtils.formatDate(cals.get(i).getTime(),"yyyy-MM-dd HH:mm:ss"));
}*/
}