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Java Deque pollFirst()用法及代碼示例


Java Deque 接口的 pollFirst() 方法用於檢索和刪除雙端隊列的第一個元素。如果給定的雙端隊列為空，則該方法可能返回 null。

用法:

public E pollFirst()

參數：

NA

返回：

上麵的方法用於返回deque的頭部。另一方麵，如果雙端隊列為空，則該方法可能返回 null。

例子1

import java.util.ArrayDeque;
import java.util.Deque;
public class JavaDequepollFirstExample1 {
   public static void main(String[] args) {
	   Deque<Character> deque = new ArrayDeque<>();
		deque.offer('q');
		deque.offer('u');
		deque.offer('e');
		deque.offer('r');
		deque.offer('y');
		Character val = deque.pollFirst();			
	System.out.println("The first character is given as:"+val);
	System.out.println("The remaining deque is:");
		for (Character character:deque) {
			System.out.println(character);
		}   	
	}
}

輸出：

The first character is given as:q
The remaining deque is:
u
e
r
y

例子2

import java.util.ArrayDeque;
import java.util.Deque;
public class JavaDequepollFirstExample2 {
   public static void main(String[] args) {
	   Deque<String> deque = new ArrayDeque<>();
		deque.offer("Hello");
		deque.offer(" ");
		deque.offer("World");
		String val = deque.pollFirst();
		System.out.println("The first string is given as:"+val);
		System.out.println("The remaining deque is:"+deque);
	}
}

輸出：

The first string is given as:Hello
The remaining deque is:[ , World]

例子3

import java.util.ArrayDeque;
import java.util.Deque;
public class JavaDequepollFirstExample3 {
   public static void main(String[] args) {
	 Deque<Long> deque = new ArrayDeque<>();
	    deque.offer(88l);
	    deque.offer(78l);
	    deque.offer(67l);
	   Long val = deque.peek();
	System.out.println("The first long value is given as:"+val);
	System.out.println("The resultant deque is:"+deque);  
   }

輸出：

The first long value is given as:88
The resultant deque is:[88, 78, 67]




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