Java中的 TreeSet floor() 方法及示例

Java.util.TreeSet类的floor()方法用于返回该集合中小于或等于给定元素的最大元素，如果没有这样的元素，则返回 null。

句法：

public E floor(E e)

参数：此方法将值e作为要匹配的参数。

返回值：该方法返回小于等于e的最大元素，如果不存在则返回null

异常：如果指定元素为 null 并且此集合使用自然排序，或者其比较器不允许 null 元素，则此方法抛出NullPointerException

下面是说明floor()方法的示例

示例 1：

// Java program to demonstrate
// floor() method
// for Integer value
  
import java.util.*;
  
public class GFG1 {
    public static void main(String[] argv) throws Exception
    {
        try {
  
            // create tree set object
            TreeSet treeadd = new TreeSet();
  
            // populate the TreeSet using add() method
            treeadd.add(10);
            treeadd.add(20);
            treeadd.add(30);
            treeadd.add(40);
  
            // Print the TreeSet
            System.out.println("TreeSet: " + treeadd);
  
            // getting the floor value for 25
            // using floor() method
            int value = treeadd.floor(25);
  
            // printing the floor value
            System.out.println("Floor value for 25: "
                               + value);
        }
  
        catch (NullPointerException e) {
            System.out.println("Exception thrown : " + e);
        }
    }
}

输出：

TreeSet: [10, 20, 30, 40]
Floor value for 25: 20

示例 2：对于NullPointerException

// Java program to demonstrate
// floor() method
// for NullPointerException
  
import java.util.*;
  
public class GFG1 {
    public static void main(String[] argv)
        throws Exception
    {
        try {
  
            // create tree set object
            TreeSet treeadd = new TreeSet();
  
            // populate the TreeSet using add() method
            treeadd.add(10);
            treeadd.add(20);
            treeadd.add(30);
            treeadd.add(40);
  
            // Print the TreeSet
            System.out.println("TreeSet: " + treeadd);
  
            // getting the floor value for null
            // using floor() method
            System.out.println("Trying to get"
                               + " the floor value"
                               + " for null");
  
            int value = treeadd.floor(null);
  
            // printing the floor value
            System.out.println("Floor value for 25: "
                               + value);
        }
  
        catch (NullPointerException e) {
            System.out.println("Exception thrown : " + e);
        }
    }
}

输出：

TreeSet: [10, 20, 30, 40]
Trying to get the floor value for null
Exception thrown : java.lang.NullPointerException