Java中的 AbstractCollection contains() 方法及示例

Java AbstractCollection的contains()方法用于检查集合中是否存在元素。它将元素作为参数，如果元素存在于集合中，则返回 True。
句法：

AbstractCollection.contains(Object element)

参数：参数元素是集合类型。该参数指的是集合中需要检查其出现的元素。
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。
下面的程序说明了Java.util.AbstractCollection.contains() 方法：
方案一：

Java

// Java code to illustrate boolean contains()
 
import java.util.*;
import java.util.AbstractCollection;
 
public class AbstractCollectionDemo {
    public static void main(String args[])
    {
 
        // Creating an empty Collection
        AbstractCollection
            abs = new LinkedList();
 
        // Use add() method to add
        // elements in the collection
        abs.add("Geeks");
        abs.add("for");
        abs.add("Geeks");
        abs.add("10");
        abs.add("20");
 
        // Displaying the collection
        System.out.println("Abstract Collection:"
                           + abs);
 
        // Check if the collection contains "Hello"
        System.out.println("\nDoes the Collection"
                           + " contains 'Hello': "
                           + abs.contains("Hello"));
 
        // Check if the Collection contains "20"
        System.out.println("Does the collection"
                           + " contains '20': "
                           + abs.contains("20"));
 
        // Check if the Collection contains "Geeks"
        System.out.println("Does the Collection"
                           + " contains 'Geeks': "
                           + abs.contains("Geeks"));
    }
}

输出：

Abstract Collection:[Geeks, for, Geeks, 10, 20]

Does the Collection contains 'Hello': false
Does the collection contains '20': true
Does the Collection contains 'Geeks': true

方案二：

Java

// Java code to illustrate boolean contains()
 
import java.util.*;
import java.util.AbstractCollection;
 
public class AbstractCollectionDemo {
    public static void main(String args[])
    {
 
        // Creating an empty Collection
        AbstractCollection
            abs = new TreeSet();
 
        // Use add() method to add
        // elements in the collection
        abs.add("Geeks");
        abs.add("for");
        abs.add("Geeks");
        abs.add("TreeSet");
        abs.add("20");
 
        // Displaying the collection
        System.out.println("Abstract Collection:"
                           + abs);
 
        // Check if the collection contains "TreeSet"
        System.out.println("\nDoes the Collection "
                           + "contains 'TreeSet': "
                           + abs.contains("TreeSet"));
 
        // Check if the collection contains "Hello"
        System.out.println("\nDoes the Collection"
                           + " contains 'Hello': "
                           + abs.contains("Hello"));
 
        // Check if the Collection contains "20"
        System.out.println("Does the collection"
                           + " contains '20': "
                           + abs.contains("20"));
 
        // Check if the Collection contains "Geeks"
        System.out.println("Does the Collection"
                           + " contains 'Geeks': "
                           + abs.contains("Geeks"));
    }
}

输出：

Abstract Collection:[20, Geeks, TreeSet, for]

Does the Collection contains 'TreeSet': true

Does the Collection contains 'Hello': false
Does the collection contains '20': true
Does the Collection contains 'Geeks': true