Java LinkedList公共int indexOf（Object o）方法（带示例）

LinkedList公共int indexOf(Object o)方法 (LinkedList public int indexOf(Object o) method)

This method is available in package java.util.LinkedList.indexOf(Object o).
软件包java.util.LinkedList.indexOf(Object o)中提供了此方法。
This method is used to return the position or index of the first occurrence of the specified object of the linked list.
此方法用于返回链表中指定对象首次出现的位置或索引。
In this method it returns -1 in two cases first will be if the element doesn't exist in the list then it returns -1 and second will be if list empty.
在此方法中，它在两种情况下返回-1 ，首先是元素在列表中不存在，然后返回-1 ，第二种情况是如果列表为空。

Syntax:

句法：

    public int indexOf(Object o){
}

Parameter(s):

参数：

We can pass only one object as a parameter in the method of the linked list.

在链表的方法中，我们只能传递一个对象作为参数。

Return value:

返回值：

The return type of this method is int type (i.e. number type ) that means this method returns the index of the first occurrence of the element after execution else returns -1.

此方法的返回类型为int类型(即数字类型)，这意味着此方法在执行后返回第一次出现的元素的索引，否则返回-1 。

Java程序演示LinkedList indexOf(Object o)方法的示例 (Java program to demonstrate example of LinkedList indexOf(Object o) method)

Case 1: Linked List with unique elements

情况1：具有唯一元素的链接列表

import java.util.LinkedList;
public class LinkList {
public static void main(String[] args) {
LinkedList list = new LinkedList();
// use add() method to add elements in the list 
list.add(10);
list.add(20);
list.add(30);
list.add(40);
list.add(50);
//  Current list Output
System.out.println("The Current list is:" + list);
// We will find the position of element 30 in the linked list
System.out.println("The position of element 30 in the list is:" + list.indexOf(30));
}
}

Output

输出量

D:\Programs>javac LinkList.java
D:\Programs>java LinkList
The Current list is:[10, 20, 30, 40, 50]
The position of element 30 in the list is:2

Case 2: Linked List with duplicate elements

情况2：具有重复元素的链表

import java.util.LinkedList;
public class LinkList {
public static void main(String[] args) {
LinkedList list = new LinkedList();
// use add() method to add elements in the list 
list.add(10);
list.add(20);
list.add(30);
list.add(20);
list.add(40);
list.add(20);
list.add(50);
//  Current list Output
System.out.println("The Current list is:" + list);
// We will find the position of element 20 in the linked list 
//and here 20 comes thrice in a list so it will return 
// index of first occurrence 
System.out.println("The position of element 20 in the list is:" + list.indexOf(20));
}
}

Output

输出量

D:\Programs>javac LinkList.java
D:\Programs>java LinkList
The Current list is:[10, 20, 30, 20, 40, 20, 50]
The position of element 30 in the list is:1