java treeset subset_Java TreeSet subSet()用法及代码示例
java.util.TreeSet.subSet()用于返回参数中提到的范围内的现有TreeSet的子集。该方法接受一个上限和一个下限，并返回范围内提到的所有元素。如果元素存在于集合中，则包括下限，而排除上限。本质上，它使子集大于等于下限，并且严格小于上元素。
用法:
TreeSettree_set.subSet(Object low_element, Object up_element)
参数：
low_element：这是TreeSet的类型，它定义了评估子集的下限或起始元素。该元素包含在子集中。
up_element：这是TreeSet的类型，它定义子集要评估的上限或最后一个元素。该元素从子集中排除。
返回值：该方法返回在给定参数范围内提到的TreeSet类型的子集。
以下程序说明了java.util.TreeSet.subSet()方法：
程序1：
// Java code to illustrate subSet() method
import java.io.*;
import java.util.Iterator;
import java.util.TreeSet;
public class Tree_Set_Demo {
public static void main(String[] args)
{
// Creating an empty TreeSet
TreeSet tree_set = new TreeSet();
// Adding the elements using add()
tree_set.add(5);
tree_set.add(1);
tree_set.add(50);
tree_set.add(10);
tree_set.add(20);
tree_set.add(6);
tree_set.add(20);
tree_set.add(18);
tree_set.add(9);
tree_set.add(30);
// Creating the subset tree
TreeSet sub_set = new TreeSet();
// Limiting the values till 5
sub_set = (TreeSet)tree_set.subSet(6, 30);
// Creating an Iterator
Iterator iterate;
iterate = sub_set.iterator();
// Displaying the tree set data
System.out.println("The resultant values within the sub set: ");
// Iterating through the subset
while (iterate.hasNext()) {
System.out.println(iterate.next() + " ");
}
}
}
输出：
The resultant values within the sub set:
6
9
10
18
20
程序2：
// Java code to illustrate subSet() method when TreeSet
// contains elements of String type
import java.io.*;
import java.util.Iterator;
import java.util.TreeSet;
public class Tree_Set_Demo {
public static void main(String[] args)
{
// Creating an empty TreeSet
TreeSet tree_set = new TreeSet();
// Adding the elements using add()
tree_set.add("Welcome");
tree_set.add("To");
tree_set.add("Geek");
tree_set.add("4");
tree_set.add("Geeks");
tree_set.add("TreeSet");
// Creating the subset tree
TreeSet sub_set = new TreeSet();
// Limiting the values till 5
sub_set = (TreeSet)tree_set.subSet("4", "TreeSet");
// Creating an Iterator
Iterator iterate;
iterate = sub_set.iterator();
// Displaying the tree set data
System.out.println("The resultant values within the sub set: ");
// Iterating through the subset
while (iterate.hasNext()) {
System.out.println(iterate.next() + " ");
}
}
}
输出：
The resultant values within the sub set:
4
Geek
Geeks
To