从 Java 树形图
中获取子地图、头地图和尾地图
原文:https://www . geesforgeks . org/get-submap-hean map-and-tail map-from-Java-tree map/
树状图是用 Java 中的抽象地图类实现地图界面和导航地图。可以在树图中使用各种构造函数来维护其键的排序。
A. subMap()方法的树形图
Java 中的 subMap()方法用于返回由参数中指定范围的键定义的映射的一部分或多个部分。
语法:
newTreeMap = oldTreeMap.subMap(startKey,endKey)
- 开始键:地图的起点或下端，包括要考虑的点。
- 结束键:地图的端点或更高端，不包括要考虑的点。
返回类型:
Returns another map containing the portion of the map within the specified range.
实现:
T5】Java
// Java code to illustrate submap() Method
import java.util.*;
class GFG {
public static void main(String[] args)
{
TreeMap<Integer, String> tree
= new TreeMap<Integer, String>();
// Mapping String to Integer
tree.put(47, "Sashi");
tree.put(82, "Ridhi");
tree.put(66, "Himanshu");
tree.put(98, "Sarthak");
tree.put(87, "Sonika");
tree.put(85, "Ritesh");
tree.put(89, "Yogesh");
// printing the complete TreeMap
System.out.println("The original map is: \n"
+ tree);
// printing the submap from key
// 67(included) to 89(excluded)
System.out.println("The subMap is: \n"
+ tree.subMap(67, 89));
// if start key and end key are same then
// this method returns a null map
System.out.println("Empty subMap: \n"
+ tree.subMap(67, 67));
}
}
输出
The original map is:
{47=Sashi, 66=Himanshu, 82=Ridhi, 85=Ritesh, 87=Sonika, 89=Yogesh, 98=Sarthak}
The subMap is:
{82=Ridhi, 85=Ritesh, 87=Sonika}
Empty subMap:
{}
b . tree map 的 headMap()方法
树状图类的头映射()方法用于获取严格小于参数 key_value 的地图的所有对或部分。
语法:
newTreeMap = oldTreeMap.headMap(specifiedKey)
返回类型:
The method returns the portion of the map whose keys are less than the specified key.
实施:
Java 语言(一种计算机语言，尤用于创建网站)
// Java code to illustrate headmap() method
import java.util.*;
class GFG {
public static void main(String[] args)
{
TreeMap<Integer, String> tree
= new TreeMap<Integer, String>();
// Mapping String to Integer
tree.put(47, "Sashi");
tree.put(82, "Ridhi");
tree.put(66, "Himanshu");
tree.put(98, "Sarthak");
tree.put(87, "Sonika");
tree.put(85, "Ritesh");
tree.put(89, "Yogesh");
// printing the complete TreeMap
System.out.println("The original map is: \n"
+ tree);
// this will print all the key-value
// pairs which are less than 67
System.out.println("The headMap is: \n"
+ tree.headMap(67));
}
}
Output
The original map is:
{47=Sashi, 66=Himanshu, 82=Ridhi, 85=Ritesh, 87=Sonika, 89=Yogesh, 98=Sarthak}
The headMap is:
{47=Sashi, 66=Himanshu}
C. tailMap()方法的树形图
Java 中的 tailMap() 方法用于获取参数中键大于等于 from_key 的地图的一部分或视图。
语法:
newMap = oldMap.tailMap(specifiedKey)
返回类型:
This method returns a map in which keys are greater than or equal to the specified key.
实现:
T5】Java
// Java code to illustrate tailmap() Method
import java.util.*;
class GFG {
public static void main(String[] args)
{
TreeMap<Integer, String> tree
= new TreeMap<Integer, String>();
// Mapping String to Integer
tree.put(47, "Sashi");
tree.put(82, "Ridhi");
tree.put(66, "Himanshu");
tree.put(98, "Sarthak");
tree.put(87, "Sonika");
tree.put(85, "Ritesh");
tree.put(89, "Yogesh");
// printing the complete TreeMap
System.out.println("The original map is: \n"
+ tree);
// this will print all the key-value pairs
// which are greater than or equal to 67
System.out.println("The tailMap is: \n"
+ tree.tailMap(67));
}
}
输出
The original map is:
{47=Sashi, 66=Himanshu, 82=Ridhi, 85=Ritesh, 87=Sonika, 89=Yogesh, 98=Sarthak}
The tailMap is:
{82=Ridhi, 85=Ritesh, 87=Sonika, 89=Yogesh, 98=Sarthak}
重要提示:subMap()、headMap()、tailMap()方法返回的地图的任何更改也将反映在原始地图中。
实现:
Java
// Combine operation on getting submap,
// headmap, and tailmap from Java TreeMap
import java.util.*;
class GFG {
public static void main(String[] args)
{
TreeMap<Integer, String> originalTree
= new TreeMap<Integer, String>();
// Mapping String to Integer
originalTree.put(82, "Ridhi");
originalTree.put(87, "Sonika");
originalTree.put(85, "Ritesh");
originalTree.put(89, "Yogesh");
originalTree.put(80, "Yashdeep");
originalTree.put(99, "Raushan");
originalTree.put(67, "Shishya");
// printing the complete TreeMap
System.out.println("The original map is: \n"
+ originalTree);
// submap from key 67(included) to 89(excluded)
Map<Integer, String> newSubMap
= originalTree.subMap(67, 89);
// doing some modification in map named
// newSubMap and this modification is going to
// be refelected in the original treemap also
newSubMap.remove(67);
// printing the original treemap to see the
// modification
System.out.println(
"The original map after remove operation is: \n"
+ originalTree);
// creating a new map named newHeadMap
Map<Integer, String> newHeadMap
= originalTree.headMap(87);
// doing some modification in map named
// newHeadMap and this modification is going to
// be refelected in the original treemap also
newHeadMap.remove(82);
// printing the original
// treemap to see the modification
System.out.println(
"The original map after remove operation: \n"
+ originalTree);
// creating a new map named newTailMap
Map<Integer, String> newTailMap
= originalTree.tailMap(85);
// doing some modification in map named
// newHeadMap and this modification is going to
// be refelected in the original treemap also
newTailMap.put(94, "Ankit");
// printing the original treemap
// to see the modification
System.out.println(
"The original map after put operation is: \n"
+ originalTree);
}
}
输出
The original map is:
{67=Shishya, 80=Yashdeep, 82=Ridhi, 85=Ritesh, 87=Sonika, 89=Yogesh, 99=Raushan}
The original map after remove operation is:
{80=Yashdeep, 82=Ridhi, 85=Ritesh, 87=Sonika, 89=Yogesh, 99=Raushan}
The original map after remove operation:
{80=Yashdeep, 85=Ritesh, 87=Sonika, 89=Yogesh, 99=Raushan}
The original map after put operation is:
{80=Yashdeep, 85=Ritesh, 87=Sonika, 89=Yogesh, 94=Ankit, 99=Raushan}
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