Definition
An array is an ordered sequence of elements. If you name a collection of a limited number of variables of the same type, the name is an array name. The variables that make up an array are called the components of the array, also called the elements of the array, and sometimes called subscript variables. The number used to distinguish the elements of an array is called a subscript. Array is a kind of form in which several elements of the same type are organized in an unordered form for the convenience of processing. These unordered collections of like data elements are called arrays.
code implementation
package com.company;
public class Array<E> {
// Generic array
private E[] data;
// Number of storage elements
private int size;
// Constructor
public Array(){
this(10);
}
//Constructor
public Array(int capacity){
data = (E[]) new Object[capacity];
size = 0;
}
// Get the number of elements in the array
public int getSize() {
return size;
}
// Get array capacity
public int getCapacity(){
return data.length;
}
// Judge whether the array is empty
public boolean isEmpty(){
return size == 0;
}
// Insert element to array header
public void addFirst(E elem){
for (int i = size; i >= 0; i--) {
data[i + 1] = data[i];
}
data[0] = elem;
size++;
}
// Add element to end of array
public void addLast(E elem){
if (size == data.length){
resize(data.length * 2);
}
data[size++] = elem;
}
// Insert element to specified location
public void add(int index, E elem){
if (size == data.length){
resize(data.length * 2);
}
if (index < 0 || index > size){
throw new IllegalArgumentException("Illegal insertion position");
}
for (int i = size - 1; i > index - 1; i--) {
data[i + 1] = data[i];
}
data[index] = elem;
size++;
}
// Get the element corresponding to the index
public E get(int index){
if (index < 0 || index >= size){
throw new IllegalArgumentException("Array Index Overflow");
}
return data[index];
}
// Get first element
public E getFirst(){
return get(0);
}
// Get last element
public E getLast(){
return get(size - 1);
}
// Modify the element corresponding to the index
public void set(int index, E elem){
if (index < 0 || index >= size){
throw new IllegalArgumentException("Illegal insertion position");
}
data[index] = elem;
}
// Determine whether the element exists
public boolean contains(E elem){
for (int i = size; i > 0; i--) {
if (data[i].equals(elem)){
return true;
}
}
return false;
}
// Find the index corresponding to the element
public int find(E elem){
for (int i = 0; i < size; i++) {
if (data[i].equals(elem)){
return i;
}
}
return -1;
}
// Delete elements of the specified index
public E remove(int index){
E ret = data[index];
for (int i = index;i < size;i++){
data[i] = data[i+1];
}
size--;
data[size] = null;
if (size == data.length / 2 && data.length /2 != 0){
resize(data.length / 2);
}
return ret;
}
// Remove element from header
public E removeFirst(){
return remove(0);
}
// Remove element from tail
public E removeLast(){
return remove(size -1);
}
// Delete specified element
public void removeElem(E elem){
int index = find(elem);
if (index != -1)
{
remove(index);
}
}
// Modify array capacity
private void resize(int newCapacity){
E[] newData = (E[]) new Object[newCapacity];
for (int i = 0; i < data.length; i++) {
newData[i] = data[i];
}
data = newData;
}
@Override
public String toString() {
StringBuilder res = new StringBuilder();
res.append(String.format("Array: size = %d，capacity = %d\n", size, data.length));
res.append('[');
for (int i = 0; i < size; i++) {
res.append(data[i]);
if (i != size - 1){
res.append(", ");
}
}
res.append(']');
return res.toString();
}
}