我没看过 其他语言版的数据结构,但觉得java的实现方法很巧妙--用类和对象来实现.基于数组的表,思想很简单就是定义一个类用来存储一组数据,我定义的是ArrayListClass类,在类中定义用来操作数组的方法.其实就是 这么简单,但具体操作起来就会遇到很多麻烦了!
我们这个ArrayListClass类中首先应该包括一个数组型的域list,用来存放数据,这样放在同一数组中数据之间就产生了位置上的联系,使对数据的操作便的简单.然而这个数组到底是什么数据类型的,我们期望这个表能用于所有的数据类型,我们不能将他单纯的固定成某一种.所以我们必须将这个数据普通化,解决的办法就是定义一个类,作为所有数据类型的超类.看这个DataElement:
public abstract class DataElement {
public abstract boolean equals(DataElement otherElement);
public abstract int compareTo(DataElement otherElement);
public abstract void makeCopy(DataElement otherElement);
public abstract DataElement getCopy();
}
将他定义成为抽象的,再在定义其他数据类型时继承并实现它,我定义了两个数据类型IntElement和StringElement:
IntElement:
public class IntElement extends DataElement {
protected int num;
//constructors
public IntElement(){
num=0;
}
public IntElement(int number){
num=number;
}
public IntElement(IntElement otherElement){
num=otherElement.num;
}
///get-set Methods
public void setNum(int number){
num=number;
}
public int getNum(){
return num;
}
/* (non-Javadoc)
* @see DataElement#equals(DataElement)
*/
public boolean equals(DataElement otherElement) {
// TODO Auto-generated method stub
IntElement newe=(IntElement)otherElement;
return (this.num==newe.num);
}
/* (non-Javadoc)
* @see DataElement#compareTo(DataElement)
*/
public int compareTo(DataElement otherElement) {
// TODO Auto-generated method stub
IntElement newe=(IntElement)otherElement;
if(this.num==newe.num)
return 0;
else if(this.num>newe.num)
return 1;
else
return -1;
}
/* (non-Javadoc)
* @see DataElement#makeCopy(DataElement)
*/
public void makeCopy(DataElement otherElement) {
// TODO Auto-generated method stub
IntElement newe=(IntElement)otherElement;
this.num=newe.num;
}
/* (non-Javadoc)
* @see DataElement#getCopy()
*/
public DataElement getCopy() {
// TODO Auto-generated method stub
IntElement newElement=new IntElement();
newElement.num=this.num;
return newElement;
}
public String toString(){
return String.valueOf(num);
}
}
StringElement:
public class StringElement extends DataElement {
/**
*
*/
private String str;
//constructors
public StringElement() {
str=null;
}
public StringElement(String string){
str=string;
}
public StringElement(StringElement otherElement){
str=otherElement.str;
}
//get-set Methods
public void setStr(String string){
str=string;
}
public String getStr(){
return str;
}
/* (non-Javadoc)
* @see DataElement#equals(DataElement)
*/
public boolean equals(DataElement otherElement) {
// TODO Auto-generated method stub
StringElement newe=(StringElement)otherElement;
return (str==newe.str);
}
/* (non-Javadoc)
* @see DataElement#compareTo(DataElement)
*/
public int compareTo(DataElement otherElement) {
// TODO Auto-generated method stub
StringElement newe=(StringElement)otherElement;
return (str.compareTo(newe.str));
}
/* (non-Javadoc)
* @see DataElement#makeCopy(DataElement)
*/
public void makeCopy(DataElement otherElement) {
// TODO Auto-generated method stub
StringElement newe=(StringElement)otherElement;
str=newe.str;
}
/* (non-Javadoc)
* @see DataElement#getCopy()
*/
public DataElement getCopy() {
// TODO Auto-generated method stub
StringElement othere=new StringElement();
othere.str=str;
return othere;
}
public String toString(){
return str;
}
}
已经定义好了数据类型,所以list的数据类型我们就可以定义为DateElement[]了,这样就可以包括所以你想要的了,只要你在用的时候定义一个DataElement的子类就行了,这正是java继承的精髓所在.我们接着定义ArrayListClass类:
protected int length;
protected int maxSize;
protected DataElement[] list;这就是它的所有域了.
接下来就是它的方法了,我们对表的操作应该有很多种,比如插入、查询、删减等等,我们要逐个的实现,具体方法不再赘述,且看最后完成代码
public abstract class ArrayListClass {
//fields
protected int length;
protected int maxSize;
protected DataElement[] list;
//defalt constructors
public ArrayListClass(){
length=0;
maxSize=100;
list=new DataElement[maxSize];
}
//constructors
public ArrayListClass(int size){
if(size<=0){
System.err.println("The arry size must be positive.Creating an array of size 100.");
maxSize=100;
}
else
maxSize=size;
length=0;
list=new DataElement[maxSize];
}
public ArrayListClass(ArrayListClass otherList){
maxSize=otherList.maxSize;
length=otherList.length;
list=new DataElement[maxSize];
for(int i=0;i<length;i++){
list[i]=otherList.list[i].getCopy();
}
}
//methods
public boolean isEmpty(){
return (length==0);
}
public boolean isFull(){
return (length==maxSize);
}
public int listSize(){
return length;
}
public int maxListSize(){
return maxSize;
}
public void print(){
for(int i=0;i<length;i++){
System.out.print(list[i]+" ");
}
System.out.println();
}
public boolean isItemAtEqual(int location,DataElement item){
return(list[location].equals(item));
}
public void insrtAt(int location,DataElement insertItem){
if(location<0||location>+maxSize){
System.out.println("The position of the item to be inserted is out of range!!");
}
else
if(length>=maxSize)
System.err.println("Can't insert in a full list!!");
else{
for(int i=length;i>location;i--){
list[i]=list[i-1];
}
list[location]=insertItem.getCopy();
length++;
}
}
public void insertEnd(DataElement insertItem){
if(length>=maxSize){
System.err.println("Can't insert in a full list!!");
}
else{
list[length]=insertItem.getCopy();
length++;
}
}
public void removeAt(int location){
if(location<0||location>=length){
System.err.println("The location you want to remove is out of range!!");
}
else{
for(int i=location;i<length-1;i++){
list[i]=list[i+1];
}
list[length]=null;
length--;
}
}
public DataElement retrieveAt(int location){
if(location<0||location>=length){
System.err.println("The location of item to be retrieved is out of range!!");
return null;
}
else{
return list[location].getCopy();
}
}
public void replacAt(int location,DataElement repItem){
if(location<0||location>=length)
System.out.println("The position of item to be replaced is out of range!!");
else
list[location]=repItem.getCopy();
}
public void clearList(){
for(int i=0;i<length;i++){
list[i]=null;
}
length=0;
System.gc();
}
public void copyList(ArrayListClass otherList){
if(this!=otherList){
for(int i=0;i<length;i++)
list[i]=null;
System.gc();
maxSize=otherList.maxSize;
length=otherList.length;
list=new DataElement[maxSize];
for(int j=0;j<length;j++)
list[j]=otherList.list[j].getCopy();
}
}
public abstract int seqSearch(DataElement seqItem);
public abstract void insert(DataElement insertItem);
public abstract void remove(DataElement removeItem);
}
看到代码的最后你回发现这个类其实是一个抽象类,为什么要这样定义呢?之所以这样我们是为了针对不同是类型:顺序表和非顺序表.不难想象他们的一些方法是存在差异的,先看一下非顺序表:
public class UnorderedArrayList extends ArrayListClass{
/**
*
*/
public UnorderedArrayList() {
super();
// TODO Auto-generated constructor stub
}
/* (non-Javadoc)
* @see ArrayListClass#seqSearch(DataElement)
*/
public int seqSearch(DataElement seqItem) {
// TODO Auto-generated method stub
int loc;
boolean found=false;
for(loc=0;loc<length;loc++)
if(list[loc].equals(seqItem))
{
found=true;
break;
}
if(found)
return loc;
else
return -1;
}
/* (non-Javadoc)
* @see ArrayListClass#insert(DataElement)
*/
public void insert(DataElement insertItem) {
// TODO Auto-generated method stub
int loc;
if(length==0)
list[length++]=insertItem.getCopy();
else
if(length==maxSize)
System.err.println("Can't insert in a full list!!");
else{
loc=seqSearch(insertItem);
if(loc==-1)
list[length++]=insertItem.getCopy();
else
System.err.println("The item to be inserted is allready in the list!!");
}
}
/* (non-Javadoc)
* @see ArrayListClass#remove(DataElement)
*/
public void remove(DataElement removeItem) {
// TODO Auto-generated method stub
int loc;
if(length==0)
System.err.println("Can't delete from a empty list!!");
else{
loc=seqSearch(removeItem);
if(loc!=-1)
removeAt(loc);
else
System.err.println("The item to be deleted is not in the list!!");
}
}
}
就是这么简单!!相信顺序表也可以轻松高顶了.
