index– the index position of the element if the element is found. -1– if the element is NOT found. 2.ArrayList.indexOf()Example The following Java program gets the first index of an object in the arraylist. In this example, we are looking for the first occurrence of the string “ale...
ArrayList<HashMap<String, Object>> list = new ArrayList<HashMap<String, Object>>(); for (int j = 0; j < 3; j++) list.add(null); HashMap<String, Object> map = new HashMap<String, Object>(); map.put("name", "jim"); map.put("year", 2009); list.add(2, map); ListView ...
The JavaArrayListclass is part of theCollection framework. TheArrayListis an implementation of a resizable array data structure that automatically grows and shrinks when elements are added or removed in the runtime, whenever required, The new elements are always added to the end of current arraylis...
Java ArrayList add(int index, E element)和set(int index, E element)两个方法的说明 一般使用List集合,估计都是使用这个ArrayList,一般呢也就是简单遍历数据和存储数据。 很少使用到add(int index, E element)和set(int index, E element)两个方法。 这两个方法,乍一看,就是在指定的位置插入一条数据。 区...
public int lastIndexOf(Object o)The lastIndexOf() method is used to get the index of the last occurrence of an element in an ArrayList object.Package : java.utilJava Platform : Java SE 8 Syntax:lastIndexOf(Object o)Parameters:NameDescription o The element whose index is to be returned....
Here, theindexOf()method successfully returns the position of element13. However, the element50doesn't exist in the arraylist. Hence, the method returns-1. Example 2: Get the Position of the First Occurrence of an Element importjava.util.ArrayList;classMain{publicstaticvoidmain(String[] args)...
问题引入:今天在使用ArrayList的add(index, element)方法向list中插入数据的时候出现数组越界异常,感觉很奇怪,list不是支持动态扩展的吗?为什么会出现越界的情况呢? 有了问题,当然要首先查看JDK源码咯: /** * Inserts the specified element at the specified position in this ...
Java ArrayList.set(int index, E element) 报IndexOutOfBoundsException lpchou 华中科技大学 计算机应用技术硕士 1 人赞同了该文章 最近有一个需求,是希望一个列表在进行处理后仍然保持和之前的顺序一样,因此我写了如下代码在指定位置添加元素(大致思路代码如下): ...
ArrayList中add(E e)与add(int index,E element)实例 import java.util.ArrayList; import java.util.List; // ArrayList中add(E e)与add(int index,E element)实例 public class TestList1 { public static void main(String[] args){ List list=new ArrayList();...
public void add(int index, Object element) This method adds the element at the given index. Example 1:importjava.util.ArrayList; 2:publicclassAddMethodExample { 3:publicstaticvoidmain(String[] args) { 4:// ArrayList of String type