Java DelayQueue put()用法及代碼示例

Java中的DelayQueue類的put(E ele)方法用於將給定元素插入延遲隊列容器。 Hetre，E是此DelayQueue容器維護的元素的類型。

句法：

public void put(E ele)

參數：此方法僅接受一個參數ele。這是將插入延遲隊列的元素。

返回值：該方法的返回類型為void，並且不返回任何值。

異常：

NullPointerException ：如果給定值為null，則拋出該異常。

以下示例程序旨在說明Java中DelayQueue的put()方法：

程序1：

// Java program to illustrate the put() 
// method in Java 
  
import java.util.concurrent.DelayQueue; 
import java.util.concurrent.Delayed; 
import java.util.concurrent.TimeUnit; 
  
public class GFG { 
    public static void main(String args[]) 
    { 
        // Create DelayQueue instance 
        DelayQueue<Delayed> queue = new DelayQueue<Delayed>(); 
  
        // Initially Delay Queue is empty 
        System.out.println("Before calling put() : "
                           + queue.isEmpty()); 
  
        // Cerate an object of type Delayed 
        Delayed ele = new Delayed() { 
            public long getDelay(TimeUnit unit) 
            { 
                return 24; // some value is returned 
            } 
  
            public int compareTo(Delayed o) 
            { 
                if (o.getDelay(TimeUnit.DAYS) >  
                              this.getDelay(TimeUnit.DAYS)) 
                    return 1; 
                else if (o.getDelay(TimeUnit.DAYS) ==   
                                this.getDelay(TimeUnit.DAYS)) 
                    return 0; 
                return -1; 
            } 
        }; 
  
        // Insert the created object to DelayQueue 
        // using the put() method 
        queue.put(ele); 
  
        // Check if DelayQueue is empty. 
        System.out.println("After calling put() : "
                           + queue.isEmpty()); 
    } 
}

輸出：

Before calling put() : true
After calling put() : false

程序2：演示NullPointerException。

// Java program to illustrate the Exception thrown 
// by put() method of DelayQueue 
  
import java.util.concurrent.DelayQueue; 
import java.util.concurrent.Delayed; 
import java.util.concurrent.TimeUnit; 
  
public class GFG { 
    public static void main(String args[]) 
    { 
        DelayQueue<Delayed> queue = new DelayQueue<Delayed>(); 
  
        try { 
            queue.put(null); 
        } 
        catch (Exception e) { 
            System.out.println(e); 
        } 
    } 
}

輸出：

java.lang.NullPointerException

參考： https://docs.oracle.com/javase/7/docs/api/java/util/concurrent/DelayQueue.html#put(E)

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