Java手动实现简单 ArrayList

接口

package com.ghgcn.chapter03.data;public interface MyList<T> {    /**     * 是否为空     * @return     */    public boolean isEmpty();    /**     * 获取大小     * @return     */    public int size();    /**     * 添加默认添加到最后     * @param e     * @return     */    public boolean add(T e);    /**     * 添加到指定位置     * @param e     * @return     */    public boolean add(int index,T e);    /**     * 获取指定位置的元素     * @param index     * @return     */    public T get(int index);    /**     * 移除指定位置的元素     * @param index     * @return     */    public boolean remove(int index);}

自定义迭代器接口

package com.ghgcn.chapter03.data;import java.util.Iterator;/** * 迭代器 * @author Administrator * */public interface MyIterator<T> {    /**     * 是否有下一下     * @return     */    public boolean hasNext();    /**     * 下一个元素     * @return     */    public T next();}

实现

package com.ghgcn.chapter03.data;public class MyArrayList<T> implements MyList<T>, MyIterator<T> {    protected int DEFAULT_SIZE = 4;    protected Object[] elements;    private int size = 0;    /**     * 迭代器使用     */    private int position = 0;    /**     * 初始化 容器大小     */    public MyArrayList() {        this.elements = new Object[DEFAULT_SIZE];    }    @Override    public boolean isEmpty() {        return size == 0;    }    @Override    public int size() {        return size;    }    @Override    public boolean add(T e) {        checkSize();        elements[size++] = e;        return true;    }    /**     * 添加到指定位置     */    @Override    public boolean add(int index, T e) {        /**         * 判断下标是否在容器之内         */        if (index < 0 || index > size) {            throw new IndexOutOfBoundsException("index: " + index + "  size: " + size);        }        /**         * 判断 空间大小是否扩容量         */        checkSize();        /**         * 将要插入位置之后的元素后移一位         */        for (int k = size - 1; k >= index; k--) {            elements[k + 1] = elements[k];        }        /**         * 赋值         */        elements[index] = e;        /**         * 量加1数         */        size++;        return true;    }    /**     * 较验证空间大小 扩容     */    private void checkSize() {        if (size >= elements.length - 1) {            Object[] tmpData = new Object[elements.length * 2];            for (int i = 0; i < elements.length - 1; i++) {                tmpData[i] = elements[i];            }            elements = tmpData;        }    }    /**     * 获取指定位置的元素     */    @Override    public T get(int index) {        rangeCheck(index);        return elementData(index);    }    /**     * 移除     */    @Override    public boolean remove(int index) {        /**         * 判断下标是否在容器之内         */        if (index < 0 || index > size) {            throw new IndexOutOfBoundsException("index:  " + index + " size:  " + size);        }        /**         * 移除元素，将index之后的元素前移         */        for (int k = index - 1; k < size - 1; k++) {            elements[index] = elements[k + 1];        }        /**         * 把最后一个元素置空         */        elements[size - 1] = null;        /**         * 数量-1         */        size--;        return true;    }    /**     * 下标检查     *      * @param index     */    private void rangeCheck(int index) {        if (index >= size)            throw new IndexOutOfBoundsException(index + "");    }    /**     * 获取指定位置的元素     *      * @param index     * @return     */    @SuppressWarnings("unchecked")    T elementData(int index) {        return (T) elements[index];    }    @Override    public boolean hasNext() {        if (position >= size || elements[position] == null) {            position=0;            return false;        } else {            return true;        }    }    @Override    public T next() {        T e = elementData(position);        position++;        return e;    }    @Override    public String toString() {        if (!this.hasNext()) {            return "[]";        }        StringBuilder sb = new StringBuilder();        sb.append("[");        while (this.hasNext()) {            sb.append(next() + " ,");        }        sb.deleteCharAt(sb.length() - 1);        sb.append("]");        return sb.toString();    }    /**     * 是否包含     * @param o     * @return     */    public int contains(Object o) {        if (o == null) {            for (int i = 0; i < size; i++) {                if(elements[i]==null){                    return i;                }            }        } else {            for (int i = 0; i < size; i++) {                if(elements[i].equals(o)){                    return i;                }            }        }        return -1;    }    /**     * 移除指定对象     * @param o     * @return     */    public boolean removeObject(Object o){        if (o == null) {            for (int i = 0; i < size; i++) {                if(elements[i]==null){                    remove(i);                    return true;                }            }        } else {            for (int i = 0; i < size; i++) {                if(elements[i].equals(o)){                    remove(i);                    return true;                }            }        }        return false;    }}

测试

package com.ghgcn.chapter03.data;import java.util.Arrays;import com.sun.source.tree.WhileLoopTree;public class MyArrayListTest1 {    public static void main(String[] args) {        MyArrayList<Integer> myArrayList = new MyArrayList<>();        myArrayList.add(5);        myArrayList.add(4);        myArrayList.add(3);        myArrayList.add(2);        myArrayList.add(6);        System.out.println("size  "+myArrayList.size());        System.out.println(Arrays.toString(myArrayList.elements));        System.out.println(" 获取指定下标的元素 \n "+myArrayList.get(0));        System.out.println(" 获取指定下标的元素 \n "+myArrayList.get(4));        myArrayList.add(0, 10);        System.out.println(Arrays.toString(myArrayList.elements));        myArrayList.remove(0);        System.out.println(Arrays.toString(myArrayList.elements));        System.out.println(myArrayList.hasNext());        System.out.println("使用定义的迭代器遍历");        while(myArrayList.hasNext()){            System.out.print(myArrayList.next()+" \t");        }        System.out.println("\n 是否包含: "+ myArrayList.contains(7));        System.out.println("\n 移除: "+ myArrayList.removeObject(5));        System.out.println("使用定义的迭代器遍历:  "+myArrayList.hasNext());        while(myArrayList.hasNext()){            System.out.print(myArrayList.next()+" \t");        }        System.out.println("\n to String: "+myArrayList.toString());    }}

结果

学习中，有问题请大家指正