Java TreeSet subSet()方法

java.util.TreeSet.subSet()用于返回参数中提到的范围内现有TreeSet的一个子集。该方法接收一个上限和一个下限，并返回该范围内提到的所有元素。如果该元素存在于集合中，那么下限将被包括在内，而上限则被排除。基本上，它接收大于等于下限且严格小于上限元素的子集。

语法

TreeSet tree_set.subSet(Object low_element, Object up_element)

参数

• low_element。 这是TreeSet的类型，定义了子集的下限或起始元素，从这里开始评估。这个元素被包含在子集中。
• up_element: 这是TreeSet的类型，定义了上限或子集被评估的最后一个元素。这个元素被排除在子集之外。

返回值： 该方法返回一个在参数给定范围内提到的TreeSet类型的子集。

下面的程序说明了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<Integer> tree_set = new TreeSet<Integer>();
  
        // 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<Integer> sub_set = new TreeSet<Integer>();
  
        // Limiting the values till 5
        sub_set = (TreeSet<Integer>)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<String> tree_set = new TreeSet<String>();
  
        // 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<String> sub_set = new TreeSet<String>();
  
        // Limiting the values till 5
        sub_set = (TreeSet<String>)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