Java uses the empty() function of the Stack class to determine whether the stack is empty

Java uses the empty() function of the Stack class to determine whether the stack is empty

Stack (Stack) is a common data structure that follows the first-in, last-out (FILO) principle. In Java, we can use the Stack class to implement the functionality of the stack. The Stack class provides a series of methods to operate the stack. One of the commonly used methods is the empty() function, which is used to determine whether the stack is empty.

In Java, the Stack class is located in the java.util package. To use this class, you need to import it first. The following is a simple example that demonstrates how to use the empty() function of the Stack class to determine whether the stack is empty:

import java.util.Stack;

public class StackExample {
    public static void main(String[] args) {
        // 创建一个堆栈对象
        Stack<Integer> stack = new Stack<>();

        // 判断堆栈是否为空
        boolean isEmpty = stack.empty();
        System.out.println("堆栈是否为空：" + isEmpty);

        // 添加元素到堆栈
        stack.push(1);
        stack.push(2);
        stack.push(3);

        // 再次判断堆栈是否为空
        isEmpty = stack.empty();
        System.out.println("堆栈是否为空：" + isEmpty);

        // 弹出元素
        int poppedElement = stack.pop();
        System.out.println("弹出的元素：" + poppedElement);

        // 弹出后再次判断堆栈是否为空
        isEmpty = stack.empty();
        System.out.println("堆栈是否为空：" + isEmpty);
    }
}

In the above example, we first create a stack object of type Integer. Then determine whether the stack is empty by calling the empty() method. At this time, because no elements have been added to the stack, the returned result is true.

Next, we added 3 elements to the stack using the push() method. Call the empty() method again to determine whether the stack is empty. At this time, because there are already elements in the stack, the returned result is false.

Then we use the pop() method to pop an element in the stack and output it. Call the empty() method again to determine whether the stack is empty. At this time, because there are still elements in the stack, the returned result is false.

Through the above example, we can see that the empty() function can easily determine whether the stack is empty. In actual development, judging whether the stack is empty is often a basic step in our stack operations, which can help us avoid NullPointerException exceptions being thrown when operating on empty stacks. Therefore, it is important to use the empty() function appropriately.

To summarize, using the empty() function of the Stack class can simply determine whether the stack is empty. When using the stack, we should develop good programming habits and determine whether the stack is empty before performing stack operations to ensure the running safety of the program.

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