【Java】之 简易ArrayList

查看ArrayList的方法们（挑选几个）

源码

package dataStructure;import java.lang.reflect.Constructor;import java.lang.reflect.Method;import java.util.ArrayList;import java.util.regex.Pattern;/** * Created by donal on 2017/2/12. *//** * 输出方法体 * Pattern p = Pattern.compile("\\w+\\."); try{ Class<?> c = Class.forName("java.util.ArrayList"); Method[] methods = c.getMethods(); Constructor[] constructors = c.getConstructors(); for(Method method : methods){ System.out.println( p.matcher(method.toString()).replaceAll("")     //去掉 包名.类名. ); } System.out.println("----------------------------------------------"); for (Constructor constructor : constructors){ System.out.println(p.matcher(constructor.toString()).replaceAll("")); } }catch (ClassNotFoundException e){ System.out.println("No such class: " + e); } */public class MyArrayList {    private static final int DEFAULT_CAPACITY = 10;    private static final Object[] EMPTY_ELEMENTDATA = {};    private static final Object[] DEFAULTCAPACITY_EMPTY_ELEMENTDATA = {};    transient Object[] elementData;    private int size;    public MyArrayList() {        this.elementData = DEFAULTCAPACITY_EMPTY_ELEMENTDATA;    }    public MyArrayList(int initialCapacity){        if (initialCapacity > 0) {            this.elementData = new Object[initialCapacity];        } else if (initialCapacity == 0) {            this.elementData = EMPTY_ELEMENTDATA;        } else {            throw new IllegalArgumentException("Illegal Capacity: "+                    initialCapacity);        }    }    private void makeSure(int capacitySize){        if (elementData == DEFAULTCAPACITY_EMPTY_ELEMENTDATA ){            elementData = new Object[DEFAULT_CAPACITY];        }else if (capacitySize > DEFAULT_CAPACITY){            throw new RuntimeException();        }    }    public boolean add(Object o){        makeSure(size + 1);        elementData[size++] = o;        return true;    }    public void add(int index, Object o){        if (index >= DEFAULT_CAPACITY)            throw new RuntimeException();        makeSure(size + 1);        System.arraycopy(elementData, index, elementData, index + 1,                size - index);        elementData[index] = o;        size++;    }    public boolean remove(Object o){        int index = -1;        for (int i = 0; i < size(); ++i){            if (elementData[i] == o){                index = i;                break;            }        }        if (index == -1)            return false;        else            remove(index);        return true;    }    public Object remove(int index){        if (index >= DEFAULT_CAPACITY)            throw new RuntimeException();        Object oldElem = elementData[index];        System.arraycopy(elementData, index, elementData, index,                size - index);        elementData[size--] = null;        return oldElem;    }    public Object get(int n){        if (n > size())            throw new RuntimeException();        return elementData[n];    }    public int indexOf(Object o){        for (int i = 0; i < size(); ++i){            if (elementData[i] == o)                return i;        }        return -1;    }    public void clear(){        for (int i = 0 ; i < size(); ++i)            elementData[i] = null;    }    public boolean contains(Object o){        for (int i = 0; i < size(); ++i){            if (elementData[i] == o)                return true;        }        return false;    }    public boolean isEmpty(){        if (size() == 0)            return true;        return false;    }    public int size(){        return size;    }    public String toString(){        StringBuilder sb = new StringBuilder();        for (int i = 0 ; i < size(); ++i){            sb.append("index : " + i + ", element : " + elementData[i] + "\n");        }        return sb.toString();    }    public static void main(String[] args) {        MyArrayList myArrayList = new MyArrayList(5);        myArrayList.add("123");        myArrayList.add("456");        myArrayList.add("789");        System.out.println(myArrayList.get(1));        System.out.println(myArrayList.size());        myArrayList.remove(2);        System.out.println(myArrayList);    }}