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最代码官方2014-05-20 18:03:44

java map按照value值来比较大小排序并且返回最终结果

package com.zuidaima.util;

import java.util.Comparator;
import java.util.HashMap;
import java.util.Map;
import java.util.TreeMap;

public class ValueComparator implements Comparator<Long> {

	Map<Long, Double> base;

	public ValueComparator(Map<Long, Double> base) {
		this.base = base;
	}

	public int compare(Long a, Long b) {
		if (base.get(a).doubleValue() >= base.get(b).doubleValue()) {
			return -1;
		} else {
			return 1;
		}
	}

	public static <K, V extends Comparable<V>> Map<K, V> sortByValues(
			final Map<K, V> map) {
		Comparator<K> valueComparator = new Comparator<K>() {
			public int compare(K k1, K k2) {
				int compare = map.get(k2).compareTo(map.get(k1));
				if (compare == 0)
					return 1;
				else
					return compare;
			}
		};
		Map<K, V> sortedByValues = new TreeMap<K, V>(valueComparator);
		sortedByValues.putAll(map);
		return sortedByValues;
	}

	public static void main(String[] args) {
		HashMap<Long, Double> map = new HashMap<Long, Double>();
		map.put(1l, 99.5);
		map.put(2l, 67.2);
		map.put(3l, 67.5);
		map.put(4l, 67.6);

		ValueComparator bvc = new ValueComparator(map);
		TreeMap<Long, Double> sorted_map = new TreeMap<Long, Double>(bvc);

		System.out.println("unsorted map: " + map);

		sorted_map.putAll(map);

		System.out.println("results: " + sorted_map);

		Map<Long, Double> sorted_map2 = sortByValues(map);
		
		System.out.println("results2: " + sorted_map2);
	}
}

输出结果:

unsorted map: {1=99.5, 2=67.2, 3=67.5, 4=67.6}
results: {1=99.5, 4=67.6, 3=67.5, 2=67.2}
results2: {1=99.5, 4=67.6, 3=67.5, 2=67.2}

 

通过key比较大小的原理类似,大家改写下就好了。enjoy it。


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