Java中的堆栈indexOf（）方法与示例

Java.util.Stack.indexOf(Object element)方法用于检查和查找堆栈中特定元素的出现。如果元素存在，则返回该元素第一次出现的索引，否则如果 Stack 不包含该元素，则返回 -1。

句法：

Stack.indexOf(Object element)

参数：此方法接受堆栈类型的强制参数元素。它指定需要在堆栈中检查其出现的元素。

返回值：此方法返回堆栈中第一次出现的元素的索引或位置。否则，如果堆栈中不存在该元素，则返回-1 。返回值是整数类型。

下面的程序说明了Java.util.Stack.indexOf() 方法：

方案一：

// Java code to illustrate indexOf()
import java.util.*;
  
public class StackDemo {
    public static void main(String args[])
    {
  
        // Creating an empty Stack
        Stack stack = new Stack();
  
        // 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

方案二：

// Java code to illustrate indexOf()
import java.util.*;
  
public class StackDemo {
    public static void main(String args[])
    {
  
        // Creating an empty Stack
        Stack stack = new Stack();
  
        // 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