Java LinkedBlockingDeque addFirst()用法及代碼示例

如果有空間，LinkedBlockingDeque的addFirst(E e)方法會將參數中傳遞的元素插入到Deque的前麵。如果LinkedBlockingDeque受容量限製並且沒有剩餘空間可插入，則它返回IllegalStateException。

用法:

public void addFirst(E e)

參數：此方法接受強製參數e，該參數是要插入LinkedBlockingDeque前麵的元素。

返回值：此方法不返回任何內容。

異常：

IllegalStateException：如果由於容量限製此時無法添加元素
NullPointerException ：如果指定的元素為null

下麵的程序說明PriorityBlockingQueue的addFirst()方法：

示例1:

// Java Program Demonstrate addFirst() 
// method of LinkedBlockingDeque 
  
import java.util.concurrent.LinkedBlockingDeque; 
import java.util.*; 
  
public class GFG { 
    public static void main(String[] args) 
        throws IllegalStateException 
    { 
  
        // create object of LinkedBlockingDeque 
        LinkedBlockingDeque<Integer> LBD 
            = new LinkedBlockingDeque<Integer>(); 
  
        // Add numbers to front of LinkedBlockingDeque 
        LBD.addFirst(7855642); 
        LBD.addFirst(35658786); 
        LBD.addFirst(5278367); 
        LBD.addFirst(74381793); 
  
        // before removing print queue 
        System.out.println("Linked Blocking Deque: " + LBD); 
    } 
}

輸出：

Linked Blocking Deque: [74381793, 5278367, 35658786, 7855642]

示例2:

// Java Program Demonstrate addFirst() 
// method of LinkedBlockingDeque 
// when it is Full 
import java.util.concurrent.LinkedBlockingDeque; 
import java.util.*; 
  
public class GFG { 
    public static void main(String[] args) 
        throws IllegalStateException 
    { 
  
        // create object of LinkedBlockingDeque 
        // size of list 
        LinkedBlockingDeque<Integer> LBD 
            = new LinkedBlockingDeque<Integer>(3); 
  
        // Add numbers to front of LinkedBlockingDeque 
        LBD.addFirst(7855642); 
        LBD.addFirst(35658786); 
        LBD.addFirst(5278367); 
  
        // it is full 
        LBD.addFirst(74381793); 
  
        // before removing print queue 
        System.out.println("Linked Blocking Deque: " + LBD); 
    } 
}

輸出：

Exception in thread "main" java.lang.IllegalStateException: Deque full
    at java.util.concurrent.LinkedBlockingDeque.addFirst(LinkedBlockingDeque.java:326)
    at GFG.main(GFG.java:23)

示例3:

// Java Program Demonstrate addFirst() 
// method of LinkedBlockingDeque 
// when nill is inserted 
  
import java.util.concurrent.LinkedBlockingDeque; 
import java.util.*; 
  
public class GFG { 
    public static void main(String[] args) 
        throws IllegalStateException 
    { 
  
        // create object of LinkedBlockingDeque 
        LinkedBlockingDeque<Integer> LBD 
            = new LinkedBlockingDeque<Integer>(); 
  
        // Add numbers to front of LinkedBlockingDeque 
        LBD.addFirst(7855642); 
        LBD.addFirst(35658786); 
        LBD.addFirst(5278367); 
  
        // NULL 
        LBD.addFirst(null); 
  
        // before removing print queue 
        System.out.println("Linked Blocking Deque: " + LBD); 
    } 
}

輸出：

Exception in thread "main" java.lang.NullPointerException
    at java.util.concurrent.LinkedBlockingDeque.offerFirst(LinkedBlockingDeque.java:342)
    at java.util.concurrent.LinkedBlockingDeque.addFirst(LinkedBlockingDeque.java:325)
    at GFG.main(GFG.java:22)

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

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