When learning the usage of map collection in java, I found serveral beneficial methods that was encountered in the daily life. Now I made a summary:
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import java.util.ArrayList;
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import java.util.Collections;
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import java.util.Comparator;
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import java.util.HashMap;
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import java.util.Iterator;
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import java.util.List;
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import java.util.Map;
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import java.util.SortedMap;
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import java.util.TreeMap;
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public class MapUtil
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{
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private static final Map<String, String> contents = new HashMap<String, String>();
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@SuppressWarnings("unchecked")
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public static void initMap()
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{
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Map testMap = new HashMap<String, String>();
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testMap.put("Albert", "Shao");
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contents.putAll(testMap);
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}
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public static void listMap()
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{
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Map<String, String> testMap = new HashMap<String, String>();
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testMap.put("Albert", "Shao");
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for (Map.Entry<String, String> entry : testMap.entrySet())
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{
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System.out.println(entry.getKey() + ":" + entry.getValue());
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}
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for (String key : testMap.keySet())
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{
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System.out.println(key + ":" + testMap.get(key));
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}
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for (String value : testMap.values())
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{
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System.out.println(value);
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}
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Iterator<Map.Entry<String, String>> keyIt = testMap.entrySet()
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.iterator();
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while (keyIt.hasNext())
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{
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Map.Entry<String, String> entry = keyIt.next();
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System.out.println(entry.getKey() + ":" + entry.getValue());
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}
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}
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public static void sort()
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{
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SortedMap<String, String> sortMap = new TreeMap<String, String>();
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sortMap.put("Pair", "four");
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sortMap.put("Apple", "two");
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sortMap.put("Grape", "one");
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sortMap.put("Banana", "three");
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sortMap.put("Apple", "five");
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System.out.println(sortMap);
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}
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public static void sortByValue()
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{
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Map<String, Integer> testMap = new HashMap<String, Integer>();
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testMap.put("Pair", 2);
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testMap.put("Apple", 1);
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testMap.put("Grape", 4);
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testMap.put("Banana", 3);
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List<Map.Entry<String, Integer>> entryList = new ArrayList<Map.Entry<String, Integer>>(
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testMap.entrySet());
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Collections.sort(entryList,
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new Comparator<Map.Entry<String, Integer>>()
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{
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public int compare(Map.Entry<String, Integer> c1,
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Map.Entry<String, Integer> c2)
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{
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return (c1.getValue() - c2.getValue());
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}
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});
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System.out.println(entryList);
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}
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public static void sortByObject()
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{
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Map<String, String> testMap = new HashMap<String, String>();
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testMap.put("Pair", "BB");
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testMap.put("Apple", "AB");
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testMap.put("Grape", "AF");
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testMap.put("Banana", "XY");
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List<Map.Entry<String, String>> entryList = new ArrayList<Map.Entry<String, String>>(
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testMap.entrySet());
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Collections.sort(entryList,
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new Comparator<Map.Entry<String, String>>()
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{
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public int compare(Map.Entry<String, String> c1,
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Map.Entry<String, String> c2)
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{
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return (c1.getValue().compareTo(c2.getValue()));
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}
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});
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System.out.println(entryList);
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}
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public static void main(String[] args)
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{
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MapUtil.listMap();
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MapUtil.sort();
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MapUtil.sortByValue();
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MapUtil.sortByObject();
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}
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}
If you want to further know about the usage of list methods, you could view my another blogs.
http://blog.csdn.net/sxb0841901116/article/details/20635267
【DateStructure】 Charnming usages of Map collection in Java,布布扣,bubuko.com
【DateStructure】 Charnming usages of Map collection in Java
原文：http://blog.csdn.net/sxb0841901116/article/details/38548907
