实现ArrayList API的Java程序
ArrayList 是列表接口的可调整大小的数组。它提供了可用于在需要时操作数组大小的方法。
ArrayList 的每个实例都有一定的容量，容量是指存储 ArrayList 中元素的大小。如果您不分配任何容量，则默认容量为 10，但如果您输入第 11 个元素，则它会根据您的要求自动增加阵列的容量，因为 ArrayList 列表是一个可增长的列表。
ArrayList 的一些操作，如 size()、isEmpty()、get()、set()、iterator() 和 ListIterator() 以恒定时间运行。 add 操作运行 n 次，n 是您调用 add 方法的次数或您在数组中添加元素的次数。
ArrayList 的构造函数：
- ArrayList() ：最初创建一个空的 ArrayList。
- ArrayList(Collection c) ：创建一个包含给定集合元素的 ArrayList。
ArrayList API 的实现：
Java
// Java Program to Implement ArrayList API
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collections;
import java.util.Iterator;
import java.util.List;
import java.util.ListIterator;
import java.util.Spliterator;
public class ArrayListIntegerExample {
public static void main(String[] args)
{
// Construct an ArrayList having default capacity 10
ArrayList array = new ArrayList<>();
// ArrayList(Collection c)
ArrayList arrayWithColl
= new ArrayList(array);
// Add elements in array
array.add(100);
array.add(120);
array.add(500);
array.add(220);
array.add(150);
// Insert the elements in specified index
// array.add(index, element);
array.add(4, 50);
// Add all the elements together
// array.addAll(collection)
List list;
list = new ArrayList(Arrays.asList(90, 20, 40, 10, 15));
array.addAll(list);
// Add all the elements in specified index
// array.addAll(index, collection)
list = new ArrayList(Arrays.asList(60, 25, 12, 16, 45));
array.addAll(2, list);
// Create shallow copy of array
ArrayList array1;
array1 = array;
// Clear all the element from the list
array.clear();
// Check whether the particular element is present
// in the list or not array.contains(object)
array1.add(100);
array1.add(120);
array1.add(500);
array1.add(220);
array1.add(150);
System.out.println("Contains 120? : "
+ array1.contains(120)); // returns true
System.out.println("Contains 200? : "
+ array1.contains(200)); // returns false
// To ensure the minimum capacity of array
// ArrayList arrayname = new ArrayList(int
// minCapacity)
ArrayList array2 = new ArrayList(10);
// Iterate through the ArrayList
System.out.println();
System.out.println("Elements of the array using enhanced for-loop : ");
array.forEach(i -> System.out.print(i + " "));
System.out.println();
// Iterator
System.out.println("Elements of the array using iterator : ");
Iterator itr = array.iterator();
while (itr.hasNext())
System.out.print(itr.next() + " ");
System.out.println();
// List Iterator
System.out.println("Elements of array using list - iterator : ");
ListIterator itr1 = array.listIterator();
while (itr1.hasNext())
System.out.print(itr1.next() + " ");
System.out.println();
// Get the particular element from specified index
// array.get(index)
System.out.println("Element at index 2 is : "
+ array.get(2));
System.out.println();
// Get the position of particular element
// array.indexOf(object)
System.out.println("Element 500 is at index position : "
+ array.indexOf(500));
System.out.println();
// Check whether list is empty or not
System.out.println("Array is empty? "
+ array.isEmpty());
System.out.println();
// Get the last index of element in array
// array.lastIndexOf(object)
System.out.println("Last index of the element 100 is : "
+ array.lastIndexOf(100));
System.out.println();
// Remove the particular element
// array.remove(index)
System.out.println("Remove the element which is at index 3 : "
+ array.remove(3));
System.out.println();
// Remove all the elements together
// array.removeAll(collection)
array.removeAll(array);
// Remove all the elements of the collection
// if condition specified the given predicate
array1.add(100);
array1.add(120);
array1.add(500);
array1.add(220);
array1.add(150);
array1.add(123);
array1.add(233);
array1.add(111);
array1.removeIf(num -> (num % 3 == 0));
System.out.println("Array element after filtering : " + array1);
System.out.println();
// Retain all the elements
array1.retainAll(array);
System.out.println("Retain the array element : "
+ array1);
System.out.println();
// Set the element at particular index
array1.set(3, 999);
System.out.println();
// Display the size of arraylist
System.out.println("Size of the array is : "
+ array1.size());
System.out.println();
// Sort the list
Collections.sort(array1);
System.out.println("Array elements after sorting : "
+ array1);
System.out.println();
// Create a late-binding
Spliterator split = array1.spliterator();
// characteristic
if (split.hasCharacteristics(Spliterator.ORDERED))
System.out.println("Ordered");
if (split.hasCharacteristics(Spliterator.SIZED))
System.out.println("Sized");
System.out.println();
// estimateSize() and getExactSizeIfKnown
System.out.println("Estimate size of arraylist is : "
+ split.estimateSize());
System.out.println("Exact size of array is : "
+ split.getExactSizeIfKnown());
System.out.println();
// trySplit
Spliterator split1 = split.trySplit();
split.forEachRemaining(i -> System.out.println(i));
System.out.println("*****");
split1.forEachRemaining(i -> System.out.println(i));
System.out.println();
// Returns a sub-list within a specified index
System.out.println("Sub-list from the index position 1 to 3 : "
+ array1.subList(1, 3));
System.out.println();
// Returns an array that contain all elements
// public Object[] toArray()
Object[] o = array1.toArray();
System.out.println("ArrayList traversal using toArray method : "
+ Arrays.toString(o));
System.out.println();
// public T[] toArray(T[] a)
Integer a[] = new Integer[array1.size()];
a = array1.toArray(a);
System.out.println(
"ArrayList traversal using toArray with argument method : "
+ Arrays.toString(a));
System.out.println();
// Trim the size to the number of elements
array1.trimToSize();
System.out.println("Array size after trimming : "
+ array1.size());
}
} 输出
Contains 120? : true
Contains 200? : false
Elements of the array using enhanced for-loop :
100 120 500 220 150
Elements of the array using iterator :
100 120 500 220 150
Elements of array using list - iterator :
100 120 500 220 150
Element at index 2 is : 500
Element 500 is at index position : 2
Array is empty? false
Last index of the element 100 is : 0
Remove the element which is at index 3 : 220
Array element after filtering : [100, 500, 220, 233]
Retain the array element : [100, 500, 220, 233]
Size of the array is : 4
Array elements after sorting : [100, 220, 500, 999]
Ordered
Sized
Estimate size of arraylist is : 4
Exact size of array is : 4
500
999
*****
100
220
Sub-list from the index position 1 to 3 : [220, 500]
ArrayList traversal using toArray method : [100, 220, 500, 999]
ArrayList traversal using toArray with argument method : [100, 220, 500, 999]
Array size after trimming : 4