HashSet类contains()方法 (HashSet Class contains() method)

• contains() method is available in java.util package.

  contains()方法在java.util包中可用。

• contains() method is used to check the existence of the given object (ob) in this HashSet.

  contains()方法用于检查此HashSet中给定对象(ob)的存在。

• contains() method is a non-static method, it is accessible with the class object only, and if we try to access the method with the class name then we will get an error.

  contains()方法是一个非静态方法，只能由类对象访问，如果尝试使用类名访问该方法，则会收到错误消息。

• contains() method does not throw an exception at the time of testing the existence of the given object.

  在测试给定对象的存在时， contains()方法不会引发异常。

Syntax:

句法：

    public boolean contains (Object ob);

Parameter(s):

参数：

• Object ob – represents the object whose existence is to be checked.

  对象ob –表示要检查其存在的对象。

Return value:

返回值：

The return type of the method is boolean, it returns true when the given object exists otherwise it returns false.

方法的返回类型为boolean ，当给定对象存在时返回true，否则返回false。

Example:

例：

// Java program to demonstrate the example 
// of boolean contains (Object ob) method of HashSet 

import java.util.*;

public class ContainsOfHashSet {
    public static void main(String[] args) {
        // Instantiates a HashSet object
        HashSet < String > hs = new HashSet < String > ();

        // By using add() method is to add
        // the given object of this
        // HashSet 
        hs.add("C");
        hs.add("C++");
        hs.add("JAVA");
        hs.add("PHP");
        hs.add("SFDC");

        // Display HashSet
        System.out.println("HashSet: " + hs);

        // By using contains() method is to 
        // check whether the given object exists
        // or not exists in this HashSet
        boolean status = hs.contains("JAVA");

        // Display Status
        System.out.println("hs.contains(JAVA): " + status);
    }
}

Output

输出量

HashSet: [JAVA, C++, C, SFDC, PHP]
hs.contains(JAVA): true

翻译自: https://www.includehelp.com/java/hashset-contains-method-with-example.aspx