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    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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