如果想要反向通過value獲得key的值,提供以下方法:

package com.jglz.qing.map;

import java.util.ArrayList;
import java.util.HashMap;
import java.util.Iterator;
import java.util.Map;
import java.util.Set;

public class MapValueGetKeyDemo {

	public static void main(String[] args) {
		Map<String, String> map = new HashMap<String, String>();
		map.put("1", "A");
		map.put("2", "A");
		map.put("3", "B");
		map.put("4", "A");
		map.put("5", "A");

		String value = "A";
		ArrayList<String> arr = FromValueGetKey(map, value);
		if (!arr.isEmpty()) {
			for (int i = 0; i < arr.size(); i++) {
				System.out.println(arr.get(i));
			}
		}
	}

	private static ArrayList<String> FromValueGetKey(Map<String, String> map,
			String value) {
		Set set = map.entrySet();
		ArrayList<String> arr = new ArrayList<String>();
		Iterator it = set.iterator();
		while (it.hasNext()) {
			Map.Entry entry = (Map.Entry) it.next();
			if (entry.getValue().equals(value)) {
				String s = (String) entry.getKey();
				arr.add(s);
			}
		}
		return arr;
	}
}
 

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