Java Stack indexOf()方法与实例

Java.util.Stack.indexOf(Object element)方法用于检查和查找某个特定元素在堆栈中的出现。如果该元素存在，则返回该元素第一次出现的索引，否则，如果堆栈中不包含该元素，则返回-1。

语法

Stack.indexOf(Object element)

参数： 该方法接受一个Stack类型的强制性参数element。它指定了需要在Stack中检查其出现的元素。

返回值： 该方法返回该元素在堆栈中第一次出现的索引或位置。否则，如果该元素在Stack中不存在，则返回-1。返回的值是整数类型的。

以下程序说明了Java.util.Stack.indexOf()方法。

程序1 :

// Java code to illustrate indexOf()
import java.util.*;
  
public class StackDemo {
    public static void main(String args[])
    {
  
        // Creating an empty Stack
        Stack<String> stack = new Stack<String>();
  
        // Use add() method to add elements in the Stack
        stack.add("Geeks");
        stack.add("for");
        stack.add("Geeks");
        stack.add("10");
        stack.add("20");
  
        // Displaying the Stack
        System.out.println("Stack: " + stack);
  
        // The first position of an element
        // is returned
        System.out.println("The first occurrence"
                           + " of Geeks is at index:"
                           + stack.indexOf("Geeks"));
        System.out.println("The first occurrence"
                           + " of 10 is at index: "
                           + stack.indexOf("10"));
    }
}

输出：

Stack: [Geeks, for, Geeks, 10, 20]
The first occurrence of Geeks is at index:0
The first occurrence of 10 is at index: 3

示例2

// Java code to illustrate indexOf()
import java.util.*;
  
public class StackDemo {
    public static void main(String args[])
    {
  
        // Creating an empty Stack
        Stack<Integer> stack = new Stack<Integer>();
  
        // Use add() method to add elements in the Stack
        stack.add(1);
        stack.add(2);
        stack.add(3);
        stack.add(10);
        stack.add(20);
  
        // Displaying the Stack
        System.out.println("Stack: " + stack);
  
        // The first position of an element
        // is returned
        System.out.println("The first occurrence"
                           + " of Geeks is at index:"
                           + stack.indexOf(2));
        System.out.println("The first occurrence"
                           + " of 10 is at index: "
                           + stack.indexOf(20));
    }
}

输出：

Stack: [1, 2, 3, 10, 20]
The first occurrence of Geeks is at index:1
The first occurrence of 10 is at index: 4