Java中的 AbstractSet contains() 方法及示例

Java AbstractSet的contains()方法用于检查元素是否存在于集合中。它将元素作为参数，如果元素存在于集合中，则返回 True。

句法：

public boolean contains(Object element)

参数：参数元素是set类型。该参数指的是集合中需要检查其出现的元素。

返回值：该方法返回一个布尔值。如果元素存在于集合中，则返回 True，否则返回 False。

下面的程序说明了 AbstractSet.contains() 方法：

方案一：

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

输出：

AbstractSet: [10, 20, Geeks, for]

Does the set contains 'Hello': false
Does the set contains '20': true
Does the set contains 'Geeks': true

方案二：

// Java code to illustrate
// AbstractSet.contains()
  
import java.util.*;
  
public class GFG {
    public static void main(String args[])
    {
  
        // Creating an empty set
        AbstractSet
            abs = new TreeSet();
  
        // Use add() method to add
        // elements in the set
        abs.add(10);
        abs.add(20);
        abs.add(30);
        abs.add(40);
        abs.add(50);
  
        // Displaying the set
        System.out.println("AbstractSet:"
                           + abs);
  
        // Check if the set contains 10
        System.out.println("\nDoes the set "
                           + "contains '10': "
                           + abs.contains(10));
  
        // Check if the set contains 50
        System.out.println("\nDoes the set"
                           + " contains '50': "
                           + abs.contains(50));
  
        // Check if the set contains 100
        System.out.println("Does the set"
                           + " contains '100': "
                           + abs.contains(100));
    }
}

输出：

AbstractSet:[10, 20, 30, 40, 50]

Does the set contains '10': true

Does the set contains '50': true
Does the set contains '100': false