极客教程Java程序 实现ArrayList API
ArrayList是一个列表接口的可调整大小的数组。它提供的方法可以在需要时用来操纵数组的大小。
ArrayList的每个实例都有一定的容量，容量意味着在ArrayList中存储元素的大小。如果你没有指定任何容量，那么默认的容量是10，但是如果你输入第11个元素，那么它会根据你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()，在恒定时间内运行。添加操作在n时间内运行，n是你调用添加方法的次数或你在数组中添加元素的次数。
ArrayList的构造函数。
1.ArrayList() :最初创建一个空的ArrayList。
2.ArrayList(Collection<? extends E> c) : 创建一个ArrayList，包含给定集合的元素。
ArrayList API的实现。
// 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<Integer> array = new ArrayList<>();
// ArrayList(Collection <? extends E> c)
ArrayList<Integer> arrayWithColl
= new ArrayList<Integer>(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<Integer> list;
list = new ArrayList<Integer>(Arrays.asList(90, 20, 40, 10, 15));
array.addAll(list);
// Add all the elements in specified index
// array.addAll(index, collection)
list = new ArrayList<Integer>(Arrays.asList(60, 25, 12, 16, 45));
array.addAll(2, list);
// Create shallow copy of array
ArrayList<Integer> 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<E> arrayname = new ArrayList<E>(int
// minCapacity)
ArrayList<Integer> array2 = new ArrayList<Integer>(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<Integer> 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<Integer> 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<Integer> 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<Integer> 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> 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