用数组实现线性表

现在开始进入数据结构的复习！数据结构中最简单的结构就是线性表，线性表又分为多种类型，这篇文章讲的是基于数组实现的线性表，说明了就是自己来实现ArrayList集合，ArrayList采用的数据结构是数组，存储的元素有序但不唯一，查找效率高，但是增删没有LinkedList的效率高。 通过这篇文章你可以知道ArrayList的基本工作方式。

设计ADT

数据结构实际上就是针对一系列数据，设计一系列针对这些数据的操作方法，由于这些数据和操作方法一般来说是共性的特征，所以我们可以使用接口来进行抽象。接口代码如下所示：

public interface ListInterface<T> {public boolean add(T newEntry);public boolean add(int newPosition,T newEntry);public T remove(int givenPosition);public void clear();public boolean replace(int givenPosition,T newEntry);public T getEntry(int givenPosition);public boolean contains(T anEntry);public int getLength();public boolean isEmpty();public boolean isFull();public void display();public Iterator<T> getIterator();}

线性表类

定义一个类，implements上面的接口，在类中数据域须为数组，实现接口中声明的操作方法来对数组中的数据进行操作。

public class array_list<T> implements ListInterface<T> {private T[] list;private int length;private static final int MAX_AIZE=10;public array_list(){this(MAX_AIZE);}public array_list(int capacity) {length=0;list=(T[]) new Object[capacity];}public void makeRoom(int newPosition){for(int i=length;i>=newPosition;i--)list[i]=list[i-1];}public void removeGap(int givenPosition){assert givenPosition>0 && givenPosition<length;for(int i=givenPosition-1;i<length-1;i++)list[i]=list[i+1];}public boolean isArrayFull() {return length==list.length;}@SuppressWarnings("unchecked")private void doubleArray(){T[] oldArray=list;list=(T[]) new Object[2*oldArray.length];System.arraycopy(oldArray, 0, list, 0, oldArray.length);}@Overridepublic boolean add(T newEntry) {if(isArrayFull())doubleArray();list[length]= newEntry;length++;return true;}@Overridepublic boolean add(int newPosition, T newEntry) {if(isArrayFull())doubleArray();makeRoom(newPosition);list[newPosition-1]= newEntry;length++;return true;}@Overridepublic T remove(int givenPosition) {T result=null;if(givenPosition>0 && givenPosition<=length){assert !isEmpty();result=list[givenPosition-1];if(givenPosition<length)removeGap(givenPosition);length--;}return result;}@Overridepublic void clear() {length=0;for(int i=0;i<list.length;i++)list[i]=null;}@Overridepublic boolean replace(int givenPosition, T newEntry) {boolean isSuccessful=true;if(givenPosition>0 && givenPosition<=length)list[givenPosition-1]= newEntry;elseisSuccessful=false;return isSuccessful;}@Overridepublic T getEntry(int givenPosition) {T result=null;if(givenPosition>0 && givenPosition<=length){assert !isEmpty();result=list[givenPosition-1];}return result;}@Overridepublic boolean contains(T anEntry) {boolean found=false;for(int i=0;!found && i<length;i++)if(anEntry.equals(list[i]))found=true;return found;}@Overridepublic int getLength() {return length;}@Overridepublic boolean isEmpty() {return length==0;}@Overridepublic boolean isFull() {//return length==entry.length;return false;}@Overridepublic void display() {Iterator iterator=getIterator();while(iterator.hasNext()){System.out.print(iterator.next()+" ");}}@Overridepublic Iterator<T> getIterator() {return new IteratorForArrayList();}private class IteratorForArrayList implements Iterator<T>{private int nextIndex;private boolean wasNextCalled;public IteratorForArrayList() {nextIndex=0;wasNextCalled=false;}@Overridepublic boolean hasNext() {return nextIndex<length;}@Overridepublic T next() {if(hasNext()){wasNextCalled=true;T nextEntry=list[nextIndex];nextIndex++;return nextEntry;}elsethrow new NoSuchElementException("");}public void remove(){if(wasNextCalled){array_list.this.remove(nextIndex);nextIndex--;wasNextCalled=false;}elsethrow new IllegalStateException("");}}}

测试代码

public class main {private static array_list<Integer> list;public static void main(String[] args) {list=new array_list<Integer>();for(int i=0;i<20;i++)list.add(i);list.display();System.out.println();list.add(16, 167);list.display();System.out.println();list.replace(3, 101);list.display();System.out.println();list.remove(6);list.display();System.out.println();System.out.println(list.contains(99));}}

测试结果

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 167 15 16 17 18 19 
0 1 101 3 4 5 6 7 8 9 10 11 12 13 14 167 15 16 17 18 19 
0 1 101 3 4 6 7 8 9 10 11 12 13 14 167 15 16 17 18 19 
false