ArrayList类

JAVA中的集合分为有序可重复的List接口和无序不可重复的set接口

实现了list接口的常用类：ArrayList类和LinkedList类。

ArrayList类底层的结构是动态数组，擅长查询。

LinkedList底层结构是链表，擅长插入删除。

ArrayList类的主要方法：

ArrayList的用法（转载）

写一个简单的模仿ArrayList类的简单类：

实现add(),remove(),get(),set()方法。

package Collection;

public class MyArrayList {
    private Object[] objs;
    private int size;
    private int lenth;
    
    public Object[] getObjs() {
        return objs;
    }
    public int getSize() {
        return size;
    }
    public int getLenth() {
        return lenth;
    }
    public void setLenth(int lenth) {
        if(lenth < 0){
            try {
                throw new Exception();
            } catch (Exception e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }
        }
        this.lenth = lenth;
    }
    public MyArrayList(){
        this.lenth = 10;
        this.objs = new Object[lenth];
    }
    public MyArrayList(int lenth) {
        if(lenth < 0){
            try {
                throw new Exception();
            } catch (Exception e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }
        }
        this.objs = new Object[lenth];
    }
    public boolean add(Object obj){
        Object[] oldObjectList = this.objs;
        if(this.size == this.objs.length){
            this.objs = new Object[2 * this.objs.length + 1];
        }
        System.arraycopy(oldObjectList, 0, this.objs, 0, this.size);
        this.objs[this.size++] = obj;
        return true;
    }
    public Object remove(int index){
        Object obj = get(index);
        Object[] oldObjectList = this.objs;
        this.objs = new Object[this.size];
        for(int i = 0; i < this.size; i++){
            if(i < index){
                this.objs[i] = oldObjectList[i];
            }else if(i >= index){
                this.objs[i] = oldObjectList[i + 1];
            }
        }    
        this.size--;
        return obj;
    }
    public Object get(int index){
        checkBound(index);
        return this.objs[index];
    }
    public Object set(int index, Object obj){
        Object old = this.objs[index];
        this.objs[index]  = obj;
        return old;
    }
    private void checkBound(int index){
        if(index < 0 || index > size){
            try {
                throw new Exception();
            } catch (Exception e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }
        }
    }
}

检测类：

package Collection;

public class test {
    public static void main(String args[]){
        MyArrayList mal = new MyArrayList();
        for(int i = 0; i < 9; i++){
            mal.add(i);
        }
        System.out.println(mal.getSize());
        for(int i = 0; i < 9; i++){
            System.out.print(mal.get(i) + " ");
        }
        System.out.println();
        mal.remove(1);
        System.out.println(mal.getSize());
        for(int i = 0; i < 8; i++){
            System.out.print(mal.get(i) + " ");
        }
        mal.set(1, 10);
        System.out.println();
        for(int i = 0; i < 8; i++){
            System.out.print(mal.get(i) + " ");
        }
    }
}

结果：

比较简单，没写注释，凑活着看吧。