Java中的DelayQueue offer()方法及其示例

DelayQueue 的 offer() 方法用于将指定元素插入延迟队列中。它与DelayQueue的add()方法类似。

语法:

public boolean offer (E e)

参数:

DelayQueue仅接受属于Delayed类型的类的元素。所以，元素E的类型应为Delayed。

返回值:

此方法不返回任何内容。

异常:

空指针异常： 如果指定的元素为null。

以下程序说明了Java中的DelayQueue offer()：

示例:

// Java程序演示DelayQueue offer()方法
 
import java.util.concurrent.*;
import java.util.*;
 
// DelayQueue的DelayObject
// 必须实现Delayed、它的getDelay()和compareTo()方法
class DelayObject implements Delayed {
 
    private String name;
    private long time;
 
    // DelayObject的构造函数
    public DelayObject(String name, long delayTime)
    {
        this.name = name;
        this.time = System.currentTimeMillis()
                    + delayTime;
    }
 
    // 实现Delayed的getDelay()方法
    @Override
    public long getDelay(TimeUnit unit)
    {
        long diff = time - System.currentTimeMillis();
        return unit.convert(diff, TimeUnit.MILLISECONDS);
    }
 
    // 实现Delayed的compareTo()方法
    @Override
    public int compareTo(Delayed obj)
    {
        if (this.time < ((DelayObject)obj).time) {
            return -1;
        }
        if (this.time > ((DelayObject)obj).time) {
            return 1;
        }
        return 0;
    }
 
    // 实现Delayed的toString()方法
    @Override
    public String toString()
    {
        return "\n{"
            + " " + name + ", time=" + time + "}";
    }
}
 
// 驱动程序类
public class GFG {
    public static void main(String[] args) throws InterruptedException
    {
 
        // 使用DelayQueue()构造函数创建DelayQueue对象
        BlockingQueue<DelayObject> DQ
            = new DelayQueue<DelayObject>();
 
        // 使用add()方法将数字添加到DelayQueue尾部
        DQ.add(new DelayObject("A", 1));
        DQ.add(new DelayObject("B", 2));
 
        // 打印延迟队列
        System.out.println("Original DelayQueue: "
                           + DQ + "\n");
 
        // 现在使用offer()方法插入元素
        DQ.offer(new DelayObject("C", 10));
        DQ.offer(new DelayObject("D", 11));
        DQ.offer(new DelayObject("E", 15));
        DQ.offer(new DelayObject("F", 17));
 
        // 打印队列
        System.out.println("After insertion DelayQueue: "
                           + DQ);
    }
}

输出:

Original DelayQueue: [
{ A, time=1545817395066}, 
{ B, time=1545817395067}]

After insertion DelayQueue: [
{ A, time=1545817395066}, 
{ B, time=1545817395067}, 
{ C, time=1545817395076}, 
{ D, time=1545817395077}, 
{ E, time=1545817395081}, 
{ F, time=1545817395083}]