E pollFirst()
描述 (Description)
java.util.ArrayDeque.pollFirst()方法检索并删除此deque的第一个element 。如果此双端队列为空,则返回null 。
声明 (Declaration)
以下是java.util.ArrayDeque.pollFirst()方法的声明
public E pollFirst()
参数 (Parameters)
NA
返回值 (Return Value)
此方法返回此双端队列的head ,如果此双端队列为空,则返回null 。
异常 (Exception)
NA
例子 (Example)
以下示例显示了java.util.ArrayDeque.pollFirst()方法的用法。
package com.iowiki;
import java.util.ArrayDeque;
import java.util.Deque;
public class ArrayDequeDemo {
public static void main(String[] args) {
// create an empty array deque with an initial capacity
Deque<Integer> deque = new ArrayDeque<Integer>(8);
// use add() method to add elements in the deque
deque.add(25);
deque.add(30);
deque.add(20);
deque.add(18);
// printing all the elements available in deque
for (Integer number : deque) {
System.out.println("Number = " + number);
}
int retval = deque.pollFirst();
System.out.println("Element removed is " + retval);
// printing all the elements available in deque after using pollFirst()
for (Integer number : deque) {
System.out.println("Number = " + number);
}
}
}
让我们编译并运行上面的程序,这将产生以下结果 -
Number = 25
Number = 30
Number = 20
Number = 18
Element removed is 25
Number = 30
Number = 20
Number = 18