Java IdentityHashMap isEmpty() 方法

7 Jan 2025 | 1 分钟阅读

Java IdentityHashMap 的 isEmpty() 方法用于检查调用它的 IdentityHashMap 是否为空。

语法

如果调用它的 IdentityHashMap 为空，则返回 true。

示例 1

import java.util.IdentityHashMap;

public class IdentityHashMapIsEmptyExample1 {
    public static void main(String[] args) {
   //Creating an object of IdentityHashMap class
   IdentityHashMap<String,Integer> map1 = new IdentityHashMap<String,Integer>(6);
   
   //Creating another object of IdentityHashMap
   IdentityHashMap<String,Integer> map2 = new IdentityHashMap<String,Integer>();
   
   //Putting key-value pairs inside map
   map1.put("Java", 1);
   map1.put("is", 2);
   map1.put("the", 3);
   map1.put("best", 4);
   map1.put("programming", 5);
   map1.put("language", 6);
 
   //Checking whether the map1 and map2 IdentityHashMap is empty or not
   System.out.println(map1.isEmpty());
   System.out.println(map2.isEmpty());
}
}

输出

false
true

示例 2

import java.util.IdentityHashMap;

class Student{
    private int roll;
    private String name;
    private int standard;
    
    public Student(int roll,String name,int standard){
        this.roll = roll;
        this.name = name;
        this.standard = standard;
    }
    
    public String disp(){
        return roll+" "+name+" "+standard;
    }
}

public class IdentityHashMapIsEmptyExample2 {
    public static void main(String[] args) {
        
        //Creating Objects of Student class
        Student stud1 = new Student(1 ,"Ram ",10);
        Student stud2 = new Student(2 ,"Shyam ",10);
        Student stud3 = new Student(3 ,"Aman ",12);
        Student stud4 = new Student(4 ,"Harsh ",12);
        Student stud5 = new Student(5 ,"Shivam",11);
        
        //Creating an instance of IdentityHashMap
        IdentityHashMap<Integer,Student> map = new IdentityHashMap<Integer,Student>(5);
        IdentityHashMap<Integer,Student> map1 = new IdentityHashMap<Integer,Student>(5);
                
        //Inserting the Student class objects into IdentityHashMap
        map.put(1,stud1);
        map.put(2,stud2);
        map.put(3,stud3);
        map.put(4,stud4);        
        //Checking if this map and map1 are empty
        System.out.println(map.isEmpty());
        System.out.println(map1.isEmpty());
}
}

输出

false
true

下一主题Java-identityhashmap-hashcode-method

Java IdentityHashMap isEmpty() 方法

语法

返回

示例 1

示例 2

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Java IdentityHashMap isEmpty() 方法

语法

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示例 1

示例 2

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