Java 集合 从TreeMap中获取子映射

在这个例子中，我们将看到如何从TreeMap获取子映射。我们正在使用TreeMap类的subMap()方法。有关详细信息，请参阅以下程序中的注释。

示例

import java.util.*;class TreeMapDemo {  public static void main(String args[]) {    // Create a TreeMap    TreeMap<String, String> treemap =             new TreeMap<String, String>();    // Put elements to the map    treemap.put("Key1", "Jack");    treemap.put("Key2", "Rick");    treemap.put("Key3", "Kate");    treemap.put("Key4", "Tom");    treemap.put("Key5", "Steve");    treemap.put("Key6", "Ram");    // Displaying TreeMap elements    System.out.println("TreeMap Contains : " + treemap);    // Getting the sub map    /* public SortedMap<K,V> subMap(K fromKey,K toKey): Returns      * a view of the portion of this map whose keys range from      * fromKey, inclusive, to toKey, exclusive.      * (If fromKey and toKey are equal, the returned map is empty.)      * The returned map is backed by this map, so changes in the      * returned map are reflected in this map, and vice-versa.      * The returned map supports all optional map operations that      * this map supports.     */    SortedMap<String, String> sortedMap = treemap.subMap("Key2","Key5");    System.out.println("SortedMap Contains : " + sortedMap);    // Removing an element from Sub Map    sortedMap.remove("Key4");    /* Displaying elements of original TreeMap after      * removing an element from the Sub Map. Since Sub Map is      * backed up by original Map, the element should be removed     * from this TreeMap too.     */    System.out.println("TreeMap Contains : " + treemap);  }}

输出：

TreeMap Contains : {Key1=Jack, Key2=Rick, Key3=Kate, Key4=Tom, Key5=Steve, Key6=Ram}SortedMap Contains : {Key2=Rick, Key3=Kate, Key4=Tom}TreeMap Contains : {Key1=Jack, Key2=Rick, Key3=Kate, Key5=Steve, Key6=Ram}