java顺序表——实现ArrayList集合

注意:此处只是实现了ArrayList部分方法
1.首先新建一个List接口,内容如下:

import java.util.ArrayList;
import java.util.Collection;
import com.jinzhi.Student;
public interface List<E> {
	// 求长度
	int size();
	// 集合内是否有元素
	boolean isEmpty();
	// 某个元素是否在集合内
	boolean contains(Object o);
	// 把集合内元素转换为数组
	Object[] toArray();
	// 向集合内添加元素
	boolean add(E e);
	// 删除集合内的某个元素
	boolean remove(Object o);
	// 删除某个位置的元素
	E remove(int index);
	// 清空集合内元素
	void clear();
	// 根据下标得到集合内某个元素
	E get(int index);
	// 在某个位置添加元素
	void add(int index, E element);
	//从index位置开始插入此集合c
	boolean addAll(int index, Collection<? extends E> c);
	//删除两个集合重复的元素
	boolean removeAll(Collection<?> c);
}

2.接着是它的实现类ArrayList:

import java.util.Arrays;
import java.util.Collection;
public class ArrayList<E> implements List<E>{
	private Object[] elementDate = new Object[0];
	private int size = 0;
	
	public ArrayList() {
	}
	public ArrayList(int length) {
		this.elementDate = new Object[length];
	}
	
	@Override
	public boolean add(E e) {
		try {
			
			if (elementDate.length == 0) {
				elementDate = new Object[2];
			}
			//如果数组中数据已满
			if (size == elementDate.length) {
				int oldLength = elementDate.length;
				//长度变为已有长度的1.5倍
				int newLength = oldLength + (oldLength >> 1);
				//创建新的数组并且把已有数据放入新数组
				elementDate = Arrays.copyOf(elementDate, newLength);
			}
			//把新元素放入数组,且长度+1
			elementDate[size++] = e;
		} catch (Exception e1) {
			// TODO Auto-generated catch block
			e1.printStackTrace();
			return false;
		}
		return false;
	}
	
	@Override
	public int size() {
		return this.size;
	}

	@Override
	public boolean isEmpty() {
		return (this.size == 0);
	}

	@Override
	public boolean contains(Object o) {
		for (int i = 0; i < size; i++) {
			if (elementDate[i] == o) {
				return true;
			}
		}
		return false;
	}

	@Override
	public Object[] toArray() {
		Object[] data = Arrays.copyOf(elementDate, size);
		return data;
	}
	
	@Override
	public boolean remove(Object o) {
		int index = -1;
		for (int i = 0; i < size; i++) {
			if (o == elementDate[i]) {
				index =i;
				break;
			}
		}
		if (index == -1) {
			return false;
		} else {
			this.remove( index);
			return true;
		}
	}

	@Override
	public E remove(int index) {
		if (index > size) {
			throw new ArrayIndexOutOfBoundsException();
		}
		Object deleteO = elementDate[index];
		for (int i = index + 1; i < size; i++) {
			elementDate[i -1] = elementDate[i];
		}
		size--;
		elementDate[size] = null;
		return (E) deleteO;
		
	}

	@Override
	public void clear() {
		size = 0;
		this.elementDate = new Object[0];
	}

	@Override
	public E get(int index) {
		if (index < 0 || index >= size) {
			throw new ArrayIndexOutOfBoundsException("下标超出范围");
		}
		return (E) this.elementDate[index];
	}

	@Override
	public void add(int index, E element) {
		if (index < 0 || index >= size) {
			throw new ArrayIndexOutOfBoundsException("下标超出范围");
		}
		if (size == elementDate.length) {
			int oldLength = elementDate.length;
			//长度变为已有长度的1.5倍
			int newLength = oldLength + (oldLength >> 1);
			//创建新的数组并且把已有数据放入新数组
			elementDate = Arrays.copyOf(elementDate, newLength);
		}
		//移动老数据
		for (int i = size; i > index; i--) {
			elementDate[i] = elementDate[i-1];
		}
		elementDate[index] = element;
		size ++;
	}

	@Override
	public boolean addAll(int index, Collection<? extends E> c) {
		
		return false;
	}

	@Override
	public boolean removeAll(Collection<?> c) {
		// TODO Auto-generated method stub
		return false;
	}
}