抽象集合是 Java 中的一个空()方法，带有示例
原文:https://www . geesforgeks . org/abstract collection-isempty-method-in-Java-with-examples/
Java 抽象集合 的 isEmpty() 方法用于检查和验证集合是否为空。如果集合为空，则返回真，否则返回假。
语法:
AbstractCollection.isEmpty()
参数:该方法不取任何参数。
返回值:如果集合为空，函数返回真，否则返回假。
下面的程序说明了 AbstractCollection.isEmpty()方法的使用:
程序 1:
// Java code to illustrate isEmpty() method
import java.util.*;
import java.util.AbstractCollection;
public class AbstractCollectionDemo {
public static void main(String args[])
{
// Creating an empty Collection
AbstractCollection<String>
abs = new TreeSet<String>();
// Use add() method to add
// elements into the Collection
abs.add("Welcome");
abs.add("To");
abs.add("Geeks");
abs.add("4");
abs.add("Geeks");
abs.add("TreeSet");
// Displaying the Collection
System.out.println("Collection: " + abs);
// Check for the empty collection
System.out.println("Is the collection empty? "
+ abs.isEmpty());
// Clearing the collection
// using clear() method
abs.clear();
// Again Checking for the empty collection
System.out.println("Is the collection empty? "
+ abs.isEmpty());
}
}
Output:
Collection: [4, Geeks, To, TreeSet, Welcome]
Is the collection empty? false
Is the collection empty? true
程序 2:
// Java code to illustrate isEmpty() method
import java.util.*;
import java.util.AbstractCollection;
public class AbstractCollectionDemo {
public static void main(String args[])
{
// Creating an empty Collection
AbstractCollection<String>
abs = new ArrayList<String>();
// Use add() method to add
// elements into the Collection
abs.add("Welcome");
abs.add("To");
abs.add("Geeks");
abs.add("4");
abs.add("Geeks");
abs.add("ArrayList");
// Displaying the Collection
System.out.println("Collection: " + abs);
// Check for the empty collection
System.out.println("Is the collection empty? "
+ abs.isEmpty());
// Clearing the collection using clear() method
abs.clear();
// Again Checking for the empty collection
System.out.println("Is the collection empty? "
+ abs.isEmpty());
}
}
Output:
Collection: [Welcome, To, Geeks, 4, Geeks, ArrayList]
Is the collection empty? false
Is the collection empty? true
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