カスタムダイナミック配列の実装

public class Array {   //E    

    private E[] data;
    private int size;//          ,               

    //    ，       capacity   Array
    public Array(int capacity){
        data = (E[])new Object[capacity];
        size = 0;
    }

    //       ，       capacity=10
    public Array(){
        this(10);
    }

    //              
    public int getSize(){
        return size;
    }

    //      
    public int getCapacity(){
        return data.length;
    }

    //          
    public boolean isEmpty(){
        return size == 0;
    }

    //size                
    //           ，       size           
    //              
    //O(1)
    //    addLast  ，  2     ，      ，      O（1） 
    public void addLast(E e){

//        if(size == data.length){
//            //               ,        
//            throw new IllegalArgumentException("Array is full");
//        }
//
//        //       data[size++] = e;
//        data[size] = e;
//        size ++;

        //  add  
        add(size,e);
    }

    //             
    //O(n)
    public void addFirst(E e){
        add(0,e);
    }

    //            
    // index          e
    //O（n/2）, O(n)
    public void add(int index, E e){
        //          index    
        if(index < 0 || index > size){
            throw new IllegalArgumentException("Required index >= 0 and index <= size");
        }

        //                        
        //  
        if(size == data.length){
            //               ,  
            resize(2 * data.length);
        }

        for(int i = size - 1; i >= index; i--){
            //          (size-1)，         (index),
            //                 
            data[i + 1] = data[i];
        }

        data[index] = e;
        size ++;
    }

    @Override
    public String toString(){
        StringBuilder res = new StringBuilder();
        res.append(String.format("Array: size = %d , capacity = %d
", 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();
    }

    //  index       
    //O(1)
    public E get(int index){
        //            ，         
        if(index < 0 || index >= size){
            throw new IllegalArgumentException("Index is Illegal");
        }
        return data[index];
    }

    //  index        e
    //O(1)
    public void set(int index, E e){
        //            ，         
        if(index < 0 || index >= size){
            throw new IllegalArgumentException("Index is Illegal");
        }

        data[index] = e;
    }

    //          e
    //O(n)
    public boolean contains(E e){
        for(int i = 0; i < size; i++){
            //if(data[i] == e){
            if(data[i].equals(e)){
                return true;
            }
        }
        return false;
    }

    //       e     ，       e，   -1
    //O(n)
    public int find(E e){
        for(int i = 0; i < size; i++){
            //if(data[i] == e){
            if(data[i].equals(e)){
                return i;
            }
        }
        return -1;
    }

    //      index     ，       
    //O（n/2） = O（n）
    public E remove(int index){
        //            ，         
        if(index < 0 || index >= size){
            throw new IllegalArgumentException("Index is Illegal");
        }

        E ret = data[index];//           ，       
        for(int i = index + 1; i < size; i++){
            //  index        ，          
            data[i - 1] = data[i];
        }

        size--;
        data[size] = null;

        //  
        //     ，  Lazy           
        //if(size == data.length / 2){
        if(size == data.length / 2 && data.length / 2 != 0){
            resize(data.length / 2);
        }
        return ret;
    }

    //           ，       
    //O(n)
    public E removeFirst(){
       return remove( 0);
    }

    //            ，       
    //O(1)
    public E removeLast(){
        return remove(size - 1);
    }

    //        e
    public void removeElement(E e){
        int index = find(e);
        if(index != -1){
            remove(index);
        }
    }

    //        
    //O(n)
    private void resize(int newCapacity){
        E[] newData = (E[])new Object[newCapacity];
        for(int i = 0; i < size; i++){
            newData[i] = data[i];
        }
        data = newData;
    }
}

public class Main1 {
    public static void main(String[] args) {
        Array arr = new Array(20);

        for(int i = 0; i < 10; i++){
            arr.addLast(i);
        }

        /*
            Array: size = 10 , capacity = 20
            [0, 1, 2, 3, 4, 5, 6, 7, 8, 9]
         */
        System.out.println(arr);

        arr.add(1,100);
        /*
            Array: size = 11 , capacity = 20
            [0, 100, 1, 2, 3, 4, 5, 6, 7, 8, 9]
         */
        System.out.println(arr);

        /*
            Array: size = 12 , capacity = 20
            [-1, 0, 100, 1, 2, 3, 4, 5, 6, 7, 8, 9]
         */
        arr.addFirst(-1);
        System.out.println(arr);

        arr.remove(2);
        /*
            Array: size = 11 , capacity = 20
            [-1, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9]
         */
        System.out.println(arr);

        arr.removeElement(4);
        /*
            Array: size = 10 , capacity = 20
            [-1, 0, 1, 2, 3, 5, 6, 7, 8, 9]
         */
        System.out.println(arr);


        arr.removeFirst();
        /*
            Array: size = 9 , capacity = 20
            [0, 1, 2, 3, 5, 6, 7, 8, 9]
         */
        System.out.println(arr);
    }
}

public class Main {
    //      
    public static void main(String[] args) {
        Array arr = new Array();

        for(int i = 0; i < 10; i++){
            arr.addLast(i);
        }

        /*
            Array: size = 10 , capacity = 20
            [0, 1, 2, 3, 4, 5, 6, 7, 8, 9]
         */
        System.out.println(arr);

        arr.add(1,100);
        /*
            Array: size = 11 , capacity = 20
            [0, 100, 1, 2, 3, 4, 5, 6, 7, 8, 9]
         */
        System.out.println(arr);

        /*
                  10    20
            Array: size = 11 , capacity = 20
            [0, 100, 1, 2, 3, 4, 5, 6, 7, 8, 9]
         */
        arr.addFirst(-1);
        System.out.println(arr);

        //arr.remove(2);
        /*
            Array: size = 11 , capacity = 20
            [-1, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9]
         */
        //System.out.println(arr);

        //arr.removeElement(4);
        /*
            Array: size = 10 , capacity = 20
            [-1, 0, 1, 2, 3, 5, 6, 7, 8, 9]
         */
        //System.out.println(arr);


        //arr.removeFirst();
        /*
            Array: size = 9 , capacity = 20
            [0, 1, 2, 3, 5, 6, 7, 8, 9]
         */
        //System.out.println(arr);
    }
}