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Java PriorityBlockingQueue toArray()用法及代碼示例


toArray()

PriorityBlockingQueue的toArray方法用於以適當的順序創建一個數組，該數組具有與此PriorityBlockingQueue相同的元素。實際上，此方法將所有元素從PriorityBlockingQueue複製到新數組。此方法充當數組和PriorityBlockingQueue之間的橋梁。

用法:

public Object[] toArray()

返回值：此方法返回一個包含PriorityBlockingQueue元素的數組。


下麵的程序說明PriorityBlockingQueue類的toArray()方法：

示例1:程序演示在PriorityBlockingQueue上使用toArray()方法從包含數字的PriorityBlockingQueue創建數字數組。

// Java Program Demonstrate toArray() 
// method of PriorityBlockingQueue 
  
import java.util.concurrent.PriorityBlockingQueue; 
public class GFG { 
  
    public static void main(String[] args) 
    { 
        // define capacity of PriorityBlockingQueue 
        int capacityOfQueue = 5; 
  
        // create object of PriorityBlockingQueue 
        PriorityBlockingQueue<Integer> PrioQueue 
            = new PriorityBlockingQueue<Integer>(capacityOfQueue); 
  
        // Add numbers to PriorityBlockingQueue 
        PrioQueue.offer(35658786); 
        PrioQueue.offer(5278367); 
        PrioQueue.offer(74381793); 
        PrioQueue.offer(87625142); 
  
        // create an array of elements of PriorityBlockingQueue 
        Object[] array = PrioQueue.toArray(); 
  
        // print elements of array 
        System.out.println("Array Contains:"); 
        for (Object i : array) { 
            System.out.print(i + " "); 
        } 
    } 
}
輸出： 
Array Contains:
5278367 35658786 74381793 87625142

示例2:程序演示在PriorityBlockingQueue上使用toArray()方法從包含字符串值的PriorityBlockingQueue創建字符串數組。

// Java Program Demonstrate toArray() 
// method of PriorityBlockingQueue 
  
import java.util.concurrent.PriorityBlockingQueue; 
import java.util.*; 
  
public class GFG { 
    public static void main(String[] args) 
    { 
  
        // define capacity of PriorityBlockingQueue 
        int capacityOfQueue = 5; 
  
        // create object of PriorityBlockingQueue which contains 
        // name of students 
        PriorityBlockingQueue<String> names 
            = new PriorityBlockingQueue<String>(capacityOfQueue); 
  
        // Add names of students of girls college 
        names.offer("Joyita"); 
        names.offer("Bristi"); 
        names.offer("Riya"); 
  
        // Create a array by calling toArray() method 
        Object[] array = names.toArray(); 
  
        // Print List of names 
        System.out.println("Queue is " + names); 
  
        // Print elements of array 
        System.out.println("The array created by toArray() is:"); 
        for (Object i : array) { 
            System.out.println(i + " "); 
        } 
    } 
}
輸出： 
Queue is [Bristi, Joyita, Riya]
The array created by toArray() is:
Bristi 
Joyita 
Riya

toArray(T[] a)

PriorityBlockingQueue的toArray(T [] a)方法用於按正確順序返回包含與該PriorityBlockingQueue元素相同的元素的數組。此方法僅在一種情況下與toArray()不同。如果PriorityBlockingQueue大小小於或等於傳遞的數組，則返回的數組的類型與參數中傳遞的數組的類型相同。否則，將分配一個與指定數組相同類型的新數組，並且該數組的大小等於此隊列的大小。此方法充當數組和集合之間的橋梁。

用法:

public <T> T[] toArray(T[] a)

參數：此方法將數組作為參數，如果隊列足夠大，則要將隊列的所有元素都複製到該數組中。否則，將為它分配一個具有相同運行時類型的新數組。

返回值：此方法返回一個包含此隊列中所有元素的數組。

異常此方法引發以下異常：


  • ArrayStoreException：當傳遞的數組與PriorityBlockingQueue的元素類型不同時。
  • NullPointerException ：如果傳遞的數組為Null。

下麵的程序說明PriorityBlockingQueue類的toArray(T [] a)方法：

示例1:該程序演示PriorityBlockingQueue上的toArray(T [] a)方法。

// Java Program Demonstrate toArray(T[] a) 
// method of PriorityBlockingQueue 
  
import java.util.concurrent.PriorityBlockingQueue; 
import java.util.concurrent.TimeUnit; 
  
public class GFG { 
  
    public static void main(String[] args) 
        throws InterruptedException 
    { 
        // define capacity of PriorityBlockingQueue 
        int capacityOfQueue = 3; 
  
        // create object of PriorityBlockingQueue 
        PriorityBlockingQueue<String> PrioQueue 
            = new PriorityBlockingQueue<String>(capacityOfQueue); 
  
        // Add names of students of girls college 
        PrioQueue.offer("Joyi"); 
        PrioQueue.offer("Rani"); 
        PrioQueue.offer("Riya"); 
  
        // Creating the array 
        String[] array = new String[capacityOfQueue]; 
  
        // Calling toArray(T[] a) method 
        Object[] ReturnArray = PrioQueue.toArray(array); 
  
        // Print queue 
        System.out.println("Queue is " + PrioQueue); 
  
        // Print elements of array passed as parameter 
        System.out.println(); 
        System.out.println("The array passed to toArray() is:"); 
        for (Object i : array) { 
            System.out.println(i); 
        } 
  
        // Print elements of array retuned by method toArray() 
        System.out.println(); 
        System.out.println("The array retuned by toArray() is:"); 
        for (Object i : ReturnArray) { 
            System.out.println(i); 
        } 
    } 
}
輸出： 
Queue is [Joyi, Rani, Riya]

The array passed to toArray() is:
Joyi
Rani
Riya

The array retuned by toArray() is:
Joyi
Rani
Riya

示例2:演示由PriorityBlockingQueue的toArray(T [] a)方法引發的異常的程序。

// Java Program Demonstrate toArray(T[] a) 
// method of PriorityBlockingQueue 
  
import java.util.concurrent.PriorityBlockingQueue; 
import java.util.concurrent.TimeUnit; 
  
public class GFG { 
  
    public static void main(String[] args) 
        throws InterruptedException 
    { 
        // define capacity of PriorityBlockingQueue 
        int capacityOfQueue = 3; 
  
        // create object of PriorityBlockingQueue 
        PriorityBlockingQueue<String> PrioQueue 
            = new PriorityBlockingQueue<String>(capacityOfQueue); 
  
        // Add names of students of girls college 
        PrioQueue.offer("Joyi"); 
        PrioQueue.offer("Rani"); 
        PrioQueue.offer("Riya"); 
  
        // Creating the array with null value 
        String[] array = null; 
  
        try { 
            // Calling toArray(T[] a) method 
            Object[] ReturnArray = PrioQueue.toArray(array); 
        } 
        catch (Exception e) { 
            System.out.println("Exception thrown:" + e); 
        } 
    } 
}
輸出： 
Exception thrown:java.lang.NullPointerException

參考：



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注：本文由純淨天空篩選整理自AmanSingh2210大神的英文原創作品 PriorityBlockingQueue toArray() method in Java。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。