### 实例
使用泛型可以让我们的数据结构放置"任何"数据类型 . 不可以是基本数据类型,只能是类对象.
~~~
public class Array<E> {
private E[] data;
private int size;
//构造函数,传入数组的容量capacity构造Array
public Array(int capacity)
{
data = (E[]) new Object[capacity];
size = 0;
}
//无参数的构造函数,默认数组的容量capacity=10
public Array()
{
this(10);
}
//获取数组的元素个数
public int getSize()
{
return this.size;
}
//获取数组容量
public int getCapacity()
{
return data.length;
}
//判断数组是否为空
public boolean isEmpty()
{
return this.size == 0;
}
//向指定位置添加元素
public void add(int index, E e)
{
if(this.size == data.length)
throw new IllegalArgumentException("Add failed .Array is full");
if(index < 0 || index > this.size)
throw new IllegalArgumentException("Add failed .Require index >= 0 and index <= size.");
for(int i = this.size - 1; i >= index; i--)
data[i + 1] = data[i];
data[index] = e;
size++;
}
//向所有元素后添加一个新元素
public void addLast(E e)
{
add(size, e);
}
//向所有元素前添加一个元素
public void addFirst(E e)
{
add(0, e);
}
@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();
}
//获取index索引位置的元素
public E get(int index)
{
if(index < 0 || index >= size)
throw new IllegalArgumentException("Get failed. Index is illegal.");
return data[index];
}
//获取最后一个元素
public E getLast()
{
return get(size - 1);
}
//获取第一个元素
public E getFirst()
{
return get(0);
}
//修改index索引位置的元素
public void set(int index, E e)
{
if(index < 0 || index >= size)
throw new IllegalArgumentException("Set failed. Index is illegal.");
data[index] = e;
}
//查找数据中是否有元素e
public Boolean contains(E e)
{
for(int i = 0; i < size; i++) {
if(data[i].equals(e)) {
return true;
}
}
return false;
}
//查找数组中元素e所在的索引,如果不存在元素e,则返回-1
public int find(E e)
{
for(int i = 0; i < size; i++) {
if(data[i].equals(e)) {
return i;
}
}
return -1;
}
//删除指定index的元素,并且返回删除的元素
public E remove(int index)
{
if(index < 0 || index >= size)
throw new IllegalArgumentException("del failed. Index is illegal .");
E element = data[index];
for(int i = index + 1; i < size; i++) {
data[i - 1] = data[i];
}
size--;
data[size] = null;
if(size == data.length / 2)
resize(data.length / 2);
return element;
}
//删除第一个元素
public E removeFirst()
{
return remove(0);
}
//删除最后一个元素
public E removeLast()
{
return remove(size - 1);
}
//从数组中删除元素e
public void removeElement(E e)
{
int index = find(e);
if(index != -1)
remove(index);
}
private void resize(int newCapacity)
{
E[] newData = (E[]) new Object[newCapacity];
for(int i = 0; i < size; i++) {
newData[i] = data[i];
}
data = newData;
}
}
~~~
