實現一個簡略ArrayList, 提供 add(), remove(), size()
沒有考慮太多方面，還請批評指正。
接口定義
import java.io.Serializable;public interface PArrayListI<T> extends Serializable{public int add(T t);public int remove(T t);public T remove(int index);public long size();public T get(int index);}
List類的實現
public class PArrayList<T> implements PArrayListI<T>{private static final int Inital_Size =10;private transient int size;private transient int eleCount;private transient float growFactor =0.5F;private transient Object[] array;public PArrayList() {this.array = new Object[Inital_Size];this.size = this.array.length;}public PArrayList( int size) {this.size = size;this.array = new Object[size];}public PArrayList( int size, float growFactor) {this.size = size;this.growFactor = growFactor;this.array = new Object[size];}@Overridepublic int add(Object t) {//添加一個元素if(capacityIsEnough()){eleCount+=1;this.array[eleCount-1]= t;return 1;}else{growUp();add(t);}return 0;}@Overridepublic int remove(Object t) { // 移除一個元素if (eleCount <= 0 || size <= 0 ) {return 0;}int index = indexOf(t);if (index<0) {//不存在return 0;}else{removeByIndex(index);eleCount-=1;return 1;}}@Overridepublic long size() {return eleCount;}@Overridepublic T get(int index) { //根據座標獲取T t = (T) this.array[index];return t;}@Overridepublic T remove(int index) { //對外暴露的根據座標移除T t = get( index);removeByIndex(index);eleCount--;return t;}private boolean capacityIsEnough(){ //是否需要擴容if (eleCount<this.array.length) {return true;}return false;}private void growUp(){ //擴容執行函數int newSize= Math.round(this.size*(1+growFactor));Object[] newArrya = new Object[newSize];int i=0;for (Object object : this.array) {newArrya[i++] = object;}}private int indexOf(Object t){ // 獲取對象的座標int index = -1;if (t==null) {int i = 0;for (Object object : array) {i++;if (object == null) {if (i <0 || i >eleCount)return -1;return i;}}}else{int i = 0;for (Object object : array) {if (t.equals(object)) {if (i <0 || i >eleCount)return -1;return i;}i++;}}return index ;}int removeByIndex(int index){ //根據座標移除if (index == eleCount-1) {//最後一個元素array[index]=null;}System.arraycopy(array, index+1, array,index , eleCount-index);//-1return 1;}}
測試類
public class TestSystemArrayCopy {public static void main(String[] args) {PArrayListI<User> list = new PArrayList<User>();User user1 = new User(1);list.add(user1);list.add(new User(2));list.add(new User(3));list.add(new User(4));list.add(new User(5));list.add(new User(6));User user7 = new User(7);list.add(user7);System.out.println("removed user:: "+list.remove(0));list.remove(user7);for (int i =0;i<list.size() ; i++) {System.out.println(list.get(i).toString());}System.out.println("size: "+list.size());}}
輸出結果:
removed user:: User [id=1, name=null, age=0, money=0.0, gender=0]User [id=2, name=null, age=0, money=0.0, gender=0]User [id=3, name=null, age=0, money=0.0, gender=0]User [id=4, name=null, age=0, money=0.0, gender=0]User [id=5, name=null, age=0, money=0.0, gender=0]User [id=6, name=null, age=0, money=0.0, gender=0]size: 5