Java.util.TreeSet.subSet()用于返回参数中提到的范围内现有TreeSet的子集。该方法采用上限和下限并返回该范围中提到的所有元素。如果元素存在于集合中并且排除上限,则包括下限。基本上,它使子集大于等于下限并且严格小于上部元素。

句法:

TreeSet tree_set.subSet(Object low_element,Object up_element)

参数:

  • low_element:这是TreeSet的类型,它定义了下限或从中计算子集的起始元素。该元素包含在子集中。
  • up_element:这是TreeSet的类型,它定义了评估子集的上限或最后一个元素。该元素从子集中排除。

返回值:该方法返回给定参数范围内提到的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

 
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