Java中的NavigableMap isEmpty()方法
使用isEmpty()方法检查Map是否为空。
让我们首先创建一个NavigableMap并向其中添加一些元素-
NavigableMap<Integer, String> n = new TreeMap<Integer, String>(); n.put(5, "Tom"); n.put(9, "John"); n.put(14, "Jamie"); n.put(1, "Tim"); n.put(4, "Jackie"); n.put(15, "Kurt"); n.put(19, "Tiger"); n.put(24, "Jacob");
现在，使用以下方法检查Map是否为空。由于我们在上面添加了一些元素，因此Map不为空-
n. isEmpty();
以下是实现isEmpty()方法的示例-
示例
import java.util.*;
public class Demo {
public static void main(String[] args) {
NavigableMap<Integer, String> n = new TreeMap<Integer, String>();
n.put(5, "Tom");
n.put(9, "John");
n.put(14, "Jamie");
n.put(1, "Tim");
n.put(4, "Jackie");
n.put(15, "Kurt");
n.put(19, "Tiger");
n.put(24, "Jacob");
System.out.println("NavigableMap elements = "+n);
System.out.println("Size = "+n.size());
System.out.println("Map is empty? " + n.isEmpty());
//删除所有元素
n.clear();
System.out.println("\nUpdated NavigableMap elements = "+n);
System.out.println("Size = "+n.size());
System.out.println("Map is empty? " + n.isEmpty());
}
}输出结果
NavigableMap elements = {1=Tim, 4=Jackie, 5=Tom, 9=John, 14=Jamie, 15=Kurt, 19=Tiger, 24=Jacob}
Size = 8
Map is empty? false
Updated NavigableMap elements = {}
Size = 0
Map is empty? True