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Java DelayQueue toArray()用法及代碼示例


DelayQueue的toArray()方法用於返回包含DelayQueue中所有元素的數組。數組中沒有任何特定順序的元素。

用法:

public Object[] toArray ()
           or
public T[] toArray (T[] a)

參數：該方法或者不接受任何參數，或者將數組T [] a作為參數，如果足夠大，該數組就是要存儲列表元素的數組。否則，將為此分配一個具有相同運行時類型的新數組。


返回值：該函數返回一個包含此列表中所有元素的數組。

異常：此方法的第一次重載不會引發任何異常。但是，第二次重載引發以下異常：

  • ArrayStoreException：如果指定數組的運行時類型不是此隊列中每個元素的運行時類型的超類型。
  • NullPointerException ：如果指定的數組為null。

以下示例程序旨在說明DelayQueue.toArray()方法：

程序1:

// Java Program Demonstrate DelayQueue toArray() method 
  
import java.util.concurrent.*; 
import java.util.*; 
  
// The DelayObject for DelayQueue 
// It must implement Delayed and 
// its getDelay() and compareTo() method 
class DelayObject implements Delayed { 
  
    private String name; 
    private long time; 
  
    // Contructor of DelayObject 
    public DelayObject(String name, long delayTime) 
    { 
        this.name = name; 
        this.time = System.currentTimeMillis() 
                    + delayTime; 
    } 
  
    // Implementing getDelay() method of Delayed 
    @Override
    public long getDelay(TimeUnit unit) 
    { 
        long diff = time - System.currentTimeMillis(); 
        return unit.convert(diff, TimeUnit.MILLISECONDS); 
    } 
  
    // Implementing compareTo() method of Delayed 
    @Override
    public int compareTo(Delayed obj) 
    { 
        if (this.time < ((DelayObject)obj).time) { 
            return -1; 
        } 
        if (this.time > ((DelayObject)obj).time) { 
            return 1; 
        } 
        return 0; 
    } 
  
    // Implementing toString() method of Delayed 
    @Override
    public String toString() 
    { 
        return "\n{"
            + " " + name + ", time=" + time + "}"; 
    } 
} 
  
// Driver Class 
public class GFG { 
    public static void main(String[] args) throws InterruptedException 
    { 
  
        // create object of DelayQueue 
        // using DelayQueue() constructor 
        BlockingQueue<DelayObject> DQ 
            = new DelayQueue<DelayObject>(); 
  
        // Add numbers to end of DelayQueue 
        // using add() method 
        DQ.add(new DelayObject("A", 1)); 
        DQ.add(new DelayObject("B", 2)); 
        DQ.add(new DelayObject("C", 3)); 
        DQ.add(new DelayObject("D", 4)); 
  
        // print queue 
        System.out.println("DelayQueue: "
                           + DQ); 
  
        // Get the array of the elements 
        // of the ArrayList 
        // using toArray() method 
        Object[] arr = DQ.toArray(); 
  
        // print the array elements 
        System.out.println("Elements of DelayQueue"
                           + " as Array: "
                           + Arrays.toString(arr)); 
    } 
}
輸出： 
DelayQueue: [
{ A, time=1546842694862}, 
{ B, time=1546842694863}, 
{ C, time=1546842694864}, 
{ D, time=1546842694865}]
Elements of DelayQueue as Array: [
{ A, time=1546842694862}, 
{ B, time=1546842694863}, 
{ C, time=1546842694864}, 
{ D, time=1546842694865}]

程序2:

// Java Program Demonstrate DelayQueue toArray() method 
  
import java.util.concurrent.*; 
import java.util.*; 
  
// The DelayObject for DelayQueue 
// It must implement Delayed and 
// its getDelay() and compareTo() method 
class DelayObject implements Delayed { 
  
    private String name; 
    private long time; 
  
    // Contructor of DelayObject 
    public DelayObject(String name, long delayTime) 
    { 
        this.name = name; 
        this.time = System.currentTimeMillis() 
                    + delayTime; 
    } 
  
    // Implementing getDelay() method of Delayed 
    @Override
    public long getDelay(TimeUnit unit) 
    { 
        long diff = time - System.currentTimeMillis(); 
        return unit.convert(diff, TimeUnit.MILLISECONDS); 
    } 
  
    // Implementing compareTo() method of Delayed 
    @Override
    public int compareTo(Delayed obj) 
    { 
        if (this.time < ((DelayObject)obj).time) { 
            return -1; 
        } 
        if (this.time > ((DelayObject)obj).time) { 
            return 1; 
        } 
        return 0; 
    } 
  
    // Implementing toString() method of Delayed 
    @Override
    public String toString() 
    { 
        return "\n{"
            + " " + name + ", time=" + time + "}"; 
    } 
} 
  
// Driver Class 
public class GFG { 
    public static void main(String[] args) throws InterruptedException 
    { 
  
        // create object of DelayQueue 
        // using DelayQueue() constructor 
        BlockingQueue<DelayObject> DQ 
            = new DelayQueue<DelayObject>(); 
  
        // Add numbers to end of DelayQueue 
        // using add() method 
        DQ.add(new DelayObject("A", 1)); 
        DQ.add(new DelayObject("B", 2)); 
        DQ.add(new DelayObject("C", 3)); 
        DQ.add(new DelayObject("D", 4)); 
  
        // print queue 
        System.out.println("DelayQueue: "
                           + DQ); 
  
        // Get the array of the elements 
        // of the DelayQueue 
        // using toArray(T[]) method 
        Delayed arr[] = new Delayed[DQ.size()]; 
        arr = DQ.toArray(arr); 
  
        // print the array elements 
        System.out.println("Elements of ArrayList"
                           + " as Array: "
                           + Arrays.toString(arr)); 
    } 
}
輸出： 
DelayQueue: [
{ A, time=1546842699503}, 
{ B, time=1546842699504}, 
{ C, time=1546842699505}, 
{ D, time=1546842699506}]
Elements of ArrayList as Array: [
{ A, time=1546842699503}, 
{ B, time=1546842699504}, 
{ C, time=1546842699505}, 
{ D, time=1546842699506}]


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注：本文由純淨天空篩選整理自ProgrammerAnvesh大神的英文原創作品 DelayQueue toArray() method in Java with Examples。非經特殊聲明，原始代碼版權歸原作者所有，本譯文未經允許或授權，請勿轉載或複製。