判断多个时间段是否重叠，并取出重叠时间段

[烙印寒冰]

问题是这样的，有多个时间段被查出来，要判断这几个时间段里面是不是有重叠，有的话要把重叠时间段返回。
比如：2010-01-01 到 2011-01-01
2010-05-01 到 2013-05-01
2010-01-01 到 2012-06-01
2008-07-01 到 2015-09-01
多个时间段是有重复时间的，应该返回重复时间为2010-05-01 到2011-01-01

[火龙果被占用了]

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

public class Main {

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

        TimeBucket[] buckets = {
                new TimeBucket( "2010-01-01" , "2011-01-01" ),
                new TimeBucket( "2010-05-01" , "2013-05-01" ),
                new TimeBucket( "2010-01-01" , "2012-06-01" ),
                new TimeBucket( "2008-07-01" , "2015-09-01" )
            };

        TimeBucket union = TimeBucket.union( buckets );

        System.out.println( union );
    }

    public static final class TimeBucket {

        private static final ThreadLocal<DateFormat> FORMATS = new ThreadLocal<DateFormat>( ) {
            @Override
            protected DateFormat initialValue() {
                return new SimpleDateFormat( "yyyy-MM-dd" );
            }
        };

        private final Date start;

        private final Date end;

        public TimeBucket(Date start, Date end) {
            if ( start.after( end ) ) {
                throw new IllegalArgumentException( "time bucket is invalid" );
            }
            this.start = start;
            this.end = end;
        }

        public TimeBucket(String start, String end) throws ParseException {
            this( parse( start ) , parse( end ) );
        }

        public TimeBucket(long startTime, long endTime) {
            this( new Date( startTime ) , new Date( endTime ) );
        }

        public static TimeBucket union(TimeBucket... buckets) {
            if ( buckets == null || buckets.length == 0 ) {
                return null;
            }
            if ( buckets.length == 1 ) {
                return buckets[ 0 ];
            }
            long start = buckets[0].getStartTime( );
            long end = buckets[0].getEndTime( );
            for ( int i = 1 ; i < buckets.length ; i++ ) {
                if ( buckets[i].getStartTime( ) > start ) {
                    start = buckets[i].getStartTime( );
                }
                if ( buckets[i].getEndTime( ) < end ) {
                    end = buckets[i].getEndTime( );
                }
            }
            if ( start > end ) {
                return null;
            }
            return new TimeBucket( start , end );
        }

        public Date getStart() {
            return start;
        }

        public Date getEnd() {
            return end;
        }

        public long getStartTime() {
            return start.getTime( );
        }

        public long getEndTime() {
            return end.getTime( );
        }

        private static Date parse(String str) throws ParseException {
            return FORMATS.get( ).parse( str );
        }

        private static String format(Date str) {
            return FORMATS.get( ).format( str );
        }

        @Override
        public String toString() {
            return "startTime=" + format(start) + ", endTime=" + format(end);
        }
    }
}

startTime=2010-05-01, endTime=2011-01-01

[烙印寒冰]

万分感谢。。