数据结构之动态数组Java实现

public class Array<E> {

private E[] data;
private int size;

//有参构造函数传入数组的容量capacity
public Array(int capacity){
data = (E[])new Object[capacity];
}

//无参构造函数数组容量默认为10
public Array(){
this(10);
}

//获取数组的容量
public int getCapacity(){
return data.length;
}

//获取数组中的元素个数
public int getSize(){
return size;
}

//返回数组是否为空
public boolean isEmpty(){
return size == 0;
}

//在所有元素后添加一个新元素
public void addLast(E e){
add(size, e);
}

//在所有元素前添加一个新元素
public void addFirst(E e){
add(0, e);
}

//在index索引位置插入一个新元素e
public void add(int index, E e){
if(index < 0 || index > size){
throw new RuntimeException("Add failed Index is out bound index = "+index);
}
if(size == data.length){
resize(2 * data.length);
}
//index位置后的元素(包括index的元素)都向后挪动一位
for(int i = size - 1; i >= index; i--){
data[i+1] = data[i];
}
data[index] = e;
size++;
}

//获取index索引位置的元素
public E get(int index){
if(index < 0 || index >= size){
throw new RuntimeException("Get failed Index is out bound index = "+index);
}
return data[index];
}

//修改index索引位置的元素为e
public void set(int index, E e){
if(index < 0 || index >= size){
throw new RuntimeException("Set failed Index is out bound index = "+index);
}
data[index] = e;
}

//查找数组中是否有元素e
public boolean contains(E e){
return find(e) != -1;
}

//查找数组中元素e所在的索引查找不到返回-1
public int find(E e){
for (int i = 0; i < size; i++) {
if(data[i].equals(e)){
return i;
}
}
return -1;
}

//从数组中删除index位置的元素 返回删除的元素
public E remove(int index){
if(index < 0 || index >= size){
throw new RuntimeException("Remove failed Index is out bound index = "+index);
}
E ret = data[index];
//index位置后的元素都向前挪动一位
for (int i = index + 1; i < size; i++) {
data[i - 1] = data[i];
}
size--;
data[size] = null;
if(size == data.length / 4 && data.length / 2 != 0){
//当实际存放的元素数量是容量的1/4就将容量修改为原来的1/2
//前提要保证data.length / 2为正整数
resize(data.length / 2);
}
return ret;
}

//从数组中删除最后一个元素 返回删除的元素
public E removeLast(){
return remove(size - 1);
}

//从数组中删除第一个元素 返回删除的元素
public E removeFirst(){
return remove(0);
}

//从数组中删除元素e
public void removeElement(E e){
int index = find(e);
if(index != -1){
remove(index);
}
}

//将数组的空间容量变成newCapacity
private void resize(int newCapacity){
E[] newData = (E[])new Object[newCapacity];
for (int i = 0; i < size; 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, getCapacity()));
res.append("[");
for (int i = 0; i < size; i++) {
res.append(data[i]);
if(i != size - 1){
res.append(",");
}
}
res.append("]");
return res.toString();
}
}

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