Java.util.TreeSet.contains()方法用于检查TreeSet中是否存在特定元素。因此，本质上，它用于检查TreeSet是否包含任何特定元素。

用法:

Tree_Set.contains(Object element)

参数：参数element 是TreeSet的类型。如果TreeSet中不存在此元素，则需要对其进行检查。

返回值：如果元素存在于集合中，则该方法返回true，否则返回False。

以下示例程序旨在说明Java.util.TreeSet.conatins()方法：

// Java code to illustrate contains() method

import java.io.*;

import java.util.TreeSet;

public class TreeSetDemo {

public static void main(String args[])

{

// Creating an empty TreeSet

TreeSet tree = new TreeSet();

// Use add() method to add elements into the Set

tree.add("Welcome");

tree.add("To");

tree.add("Geeks");

tree.add("4");

tree.add("Geeks");

tree.add("TreeSet");

// Displaying the TreeSet

System.out.println("TreeSet: " + tree);

// Check for "TreeSet" in the set

System.out.println("Does the Set contains 'TreeSet'? " +

tree.contains("TreeSet"));

// Check for "4" in the set

System.out.println("Does the Set contains '4'? " +

tree.contains("4"));

// Check if the list contains "No"

System.out.println("Does the Set contains 'No'? " +

tree.contains("No"));

}

}

输出：

TreeSet: [4, Geeks, To, TreeSet, Welcome]

Does the Set contains 'TreeSet'? true

Does the Set contains '4'? true

Does the Set contains 'No'? false