一、数据结构
数据结构由数据和结构两部分组成，就是将数据按照一定的结构组合起来，这样不同的组合方式有不同的效率，可根据需求选择不同的结构应用在相应在场景。数据结构大致
分为两类：线性结构（如数组，链表，队列，栈等），非线性结构（如树，图，表等）。本文介绍下线性结构，下章介绍非线性结构。
二、数组
数组表示一组有限个相同类型的数据的集合，顺序存储，下标从0开始，其特点是可以根据下标快速的查找到元素，但在增加和删除元素时会导致大量的数据位置的变动，即这
种情况下性能不高，故数组一般多用于查找频繁，增，删较少的情况。
下图为一个二维数组的结构图：
插入元素：
当往数组某位置上插入元素时，需要将位置后的所有元素往后移动一个位置。
删除元素：
当删除数组上的某个元素时，需要将该元素后的所有元素的位置往前移动一个位置。
下面简单实现数组中插入元素和删除元素功能：
public class ArrayDemo<T> {
private Object[] array ;
private int length = 0;
private final static int DEFAULT_CAPACITY = 10;
public ArrayDemo(){
super();
this.array = new Object[DEFAULT_CAPACITY];
this.length = DEFAULT_CAPACITY;
}
public ArrayDemo(int length){
super();
if(length < 0){
throw new IllegalArgumentException("error length:"+length);
}
this.array = new Object[length];
this.length = length;
}
public ArrayDemo(Collection<? extends T> c){
array = c.toArray();
length = c.size();
if(array.getClass() != Object[].class){
array = Arrays.copyOf(array, length, Object[].class);
}
}
/**
* 在数组array的index位置处插入一个元素t,如果已经满了，则移除最后一个元素
* @param array
* @param t
* @param indext
*/
public void insert(T t, int index){
if(null == t){
throw new NullPointerException("null Pointer!");
}
if(index < 0 || index > length-1){
throw new IndexOutOfBoundsException("index is error");
}
for(int pos = length-1; pos>index; pos--){
array[pos] = array[pos-1];
}
array[index] = t;
}
/**
* 删除指定位置上的数组元素
* @param array
* @param index
*/
public void delete(int index){
if(null == array){
throw new NullPointerException("null Pointer!");
}
int length = array.length;
if(index < 0 || index > length-1){
throw new IndexOutOfBoundsException("index is error");
}
for(int pos = index; pos < length-1; pos++){
array[pos] = array[pos+1];
}
array[length-1] = null;
}
/**
* 遍历输出数组中所有元素
*/
public void trans(){
if(null == array){
throw new NullPointerException("null Pointer!");
}
for(int pos=0; pos< length; pos++){
System.out.println(array[pos]);
}
}
}public class Person {
private String name;
private String sex;
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public String getSex() {
return sex;
}
public void setSex(String sex) {
this.sex = sex;
}
@Override
public String toString() {
return "Person [name=" + name + ", sex=" + sex + "]";
}
public Person(String name, String sex) {
super();
this.name = name;
this.sex = sex;
}
@Override
public int hashCode() {
final int prime = 31;
int result = 1;
result = prime * result + ((name == null) ? 0 : name.hashCode());
result = prime * result + ((sex == null) ? 0 : sex.hashCode());
return result;
}
@Override
public boolean equals(Object obj) {
if (this == obj)
return true;
if (obj == null)
return false;
if (getClass() != obj.getClass())
return false;
Person other = (Person) obj;
if (name == null) {
if (other.name != null)
return false;
} else if (!name.equals(other.name))
return false;
if (sex == null) {
if (other.sex != null)
return false;
} else if (!sex.equals(other.sex))
return false;
return true;
}
}测试类：
public class TestArray {
public static void main(String[] args) {
ArrayDemo<Person> array = new ArrayDemo<>();
Person p = new Person("张三", "m");
array.insert(p, 0);
array.trans();
array.delete(0);
System.out.println("---");
array.trans();
}
}
三、链表
链表是一种有序的列表。链表的内容通常存储在内存中分散的位置上。链表由节点组成，每个节点的结构都是相同的。节点分为数据域和链域，数据域顾名思义，就是存放节点
节点的内容，链域存放的是下一个节点的指针或引用。如果是双向链表的话，链域中还会有前一个节点的指针或引用。下图为单向链表各节点间的关系图。
下面来实现一个简单的链表结构
节点类：
public class Node<T> {
private T data;
private Node<T> pre;
private Node<T> next;
public Node(){
super();
this.pre = null;
this.next = null;
}
public Node(T data){
super();
this.data = data;
this.pre = null;
this.next = null;
}
public Node(T data, Node<T> pre, Node<T> next){
super();
this.data = data;
this.pre = pre;
this.next = next;
}
public T getData() {
return data;
}
public void setData(T data) {
this.data = data;
}
public Node<T> getPre() {
return pre;
}
public void setPre(Node<T> pre) {
this.pre = pre;
}
public Node<T> getNext() {
return next;
}
public void setNext(Node<T> next) {
this.next = next;
}
}
链表类
public class LinkedListDemo<T> {
private Node<T> head;//头结点
private Node<T> tail;//尾节点
private int size;//链表大小
public LinkedListDemo(){
head = new Node<T>(null, null, null);
tail = new Node<T>(null, head, null);
head.setNext(tail);
size = 0;
}
public MyIterator<T> iterator(){
return new MyIterator<T>();
}
public void add(T data){
Node<T> node = new Node<T>(data);
node.setPre(tail.getPre());
tail.getPre().setNext(node);
tail.setPre(node);
node.setNext(tail);
size++;
}
public void remove(T data){
Node<T> node = head;
while(tail != node.getNext()){
Node<T> currentNode = node.getNext();
if(currentNode.getData().equals(data)){
currentNode.getPre().setNext(currentNode.getNext());
currentNode.getNext().setPre(currentNode.getPre());
size--;
break;
}
node = currentNode;
}
}
public void print(){
Node<T> node = head;
while(tail != node.getNext()){
Node<T> currentNode = node.getNext();
System.out.println(currentNode.getData().toString());
node = currentNode;
}
}
/**
*
* 项目名： adt
* 类名： LinkedListDemo.java
* 类描述： 定义一个该链表的迭代器来访问
* 备注：
* 创建日期：2014-10-10
* 创建时间：上午12:10:46
* @param <T>
*/
@SuppressWarnings("hiding")
private class MyIterator<T> implements Iterator<T>{
@SuppressWarnings("unchecked")
private Node<T> currentNode = (Node<T>) head.getNext();//节点读取当前位置
private Node<T> returnedNode = currentNode;//返回节点的位置
@Override
public boolean hasNext() {
return currentNode == tail? false:true;
}
@Override
public T next() {
if(!hasNext()){
throw new IndexOutOfBoundsException();
}
returnedNode = currentNode;
currentNode = currentNode.getNext();
return returnedNode.getData();
}
@Override
public void remove() {
if(!hasNext()){
throw new NoSuchElementException();
}
returnedNode.getPre().setNext(returnedNode.getNext());
returnedNode.getNext().setPre(returnedNode.getPre());
returnedNode = returnedNode.getNext();
currentNode = returnedNode;
size--;
}
}
}测试类：
public class TestDemo {
public static void main(String[] args) {
LinkedListDemo<Person> list = new LinkedListDemo<Person>();
//往链表中加入10个元素
for(int i=0; i<10;i++){
Person p = new Person("zhang"+i, "m");
list.add(p);
}
list.print();
System.out.println("========");
Person p = new Person("zhang1", "m");
list.remove(p);//移除自定的元素
list.print();
System.out.println("========");
Person p1 = new Person("zhang4", "m");
Iterator<Person> iterator = list.iterator();
while(iterator.hasNext()){
Person person = iterator.next();
if(person.equals(p1)){
iterator.remove();//迭代器移除制定元素
break;
}
}
list.print();
}
}结果：
Person [name=zhang0, sex=m] Person [name=zhang1, sex=m] Person [name=zhang2, sex=m] Person [name=zhang3, sex=m] Person [name=zhang4, sex=m] Person [name=zhang5, sex=m] Person [name=zhang6, sex=m] Person [name=zhang7, sex=m] Person [name=zhang8, sex=m] Person [name=zhang9, sex=m] ======== Person [name=zhang0, sex=m] Person [name=zhang2, sex=m] Person [name=zhang3, sex=m] Person [name=zhang4, sex=m] Person [name=zhang5, sex=m] Person [name=zhang6, sex=m] Person [name=zhang7, sex=m] Person [name=zhang8, sex=m] Person [name=zhang9, sex=m] ======== Person [name=zhang0, sex=m] Person [name=zhang2, sex=m] Person [name=zhang3, sex=m] Person [name=zhang5, sex=m] Person [name=zhang6, sex=m] Person [name=zhang7, sex=m] Person [name=zhang8, sex=m] Person [name=zhang9, sex=m]
四、队列
队列数据结构类似于生活中队列，有一个很重要的特性：先进先出。即增加元素肯定是在队列的尾部添加，删除元素肯定是删除队列头部的元素。队列的实现可以用数据结构，
也可以用链表结构。
下面简单是一个用数组结构实现的队列结构：
public class QueueDemo<T> {
private Object[] object;
/**
* 队列容量
*/
private int capicity;
/**
* 队列中元素的个数
*/
private int size;
private final static int DEFAULT_CAPICAL = 10;
public QueueDemo(){
capicity = DEFAULT_CAPICAL;
object = new Object[capicity];
}
public QueueDemo(int capicity){
this.capicity = capicity;
object = new Object[this.capicity];
}
public int size(){
return size;
}
public boolean isEmpty(){
return size==0;
}
/**
* 往队列中添加元素
* @param t
*/
public void add(T t){
if(size == capicity){
throw new IndexOutOfBoundsException("queue is full");
}
object[size++]=t;
}
/**
* 移除队列中的元素
*/
public void remove(){
if(isEmpty()){
throw new IndexOutOfBoundsException("queue is empty");
}
for(int pos = 0; pos < size-1; pos++){//将整个数组往前以一个位置
object[pos] = object[pos+1];
}
size--;
}
public void clear(){
Arrays.fill(object, null);
size=0;
}
public void print(){
for(int i=0; i<size; i++){
System.out.println(object[i].toString());
}
}
}测试类：
public class TestQueue {
/**
* @param args
*/
public static void main(String[] args) {
QueueDemo<Person> queue = new QueueDemo<Person>();
for(int i=0; i<10; i++){
Person p = new Person("zhang"+i, "m");
queue.add(p);
}
queue.print();
System.out.println("=====");
while(queue.size() > 0){//依次删除队列头元素
queue.remove();
queue.print();
System.out.println("=====");
}
}
}输出：
Person [name=zhang0, sex=m] Person [name=zhang1, sex=m] Person [name=zhang2, sex=m] Person [name=zhang3, sex=m] Person [name=zhang4, sex=m] Person [name=zhang5, sex=m] Person [name=zhang6, sex=m] Person [name=zhang7, sex=m] Person [name=zhang8, sex=m] Person [name=zhang9, sex=m] ===== Person [name=zhang1, sex=m] Person [name=zhang2, sex=m] Person [name=zhang3, sex=m] Person [name=zhang4, sex=m] Person [name=zhang5, sex=m] Person [name=zhang6, sex=m] Person [name=zhang7, sex=m] Person [name=zhang8, sex=m] Person [name=zhang9, sex=m] ===== Person [name=zhang2, sex=m] Person [name=zhang3, sex=m] Person [name=zhang4, sex=m] Person [name=zhang5, sex=m] Person [name=zhang6, sex=m] Person [name=zhang7, sex=m] Person [name=zhang8, sex=m] Person [name=zhang9, sex=m] ===== Person [name=zhang3, sex=m] Person [name=zhang4, sex=m] Person [name=zhang5, sex=m] Person [name=zhang6, sex=m] Person [name=zhang7, sex=m] Person [name=zhang8, sex=m] Person [name=zhang9, sex=m] ===== Person [name=zhang4, sex=m] Person [name=zhang5, sex=m] Person [name=zhang6, sex=m] Person [name=zhang7, sex=m] Person [name=zhang8, sex=m] Person [name=zhang9, sex=m] ===== Person [name=zhang5, sex=m] Person [name=zhang6, sex=m] Person [name=zhang7, sex=m] Person [name=zhang8, sex=m] Person [name=zhang9, sex=m] ===== Person [name=zhang6, sex=m] Person [name=zhang7, sex=m] Person [name=zhang8, sex=m] Person [name=zhang9, sex=m] ===== Person [name=zhang7, sex=m] Person [name=zhang8, sex=m] Person [name=zhang9, sex=m] ===== Person [name=zhang8, sex=m] Person [name=zhang9, sex=m] ===== Person [name=zhang9, sex=m] ===== =====
五、栈
栈结构与队列类似，不过区别在于栈是先进后出的。即最先进栈的元素是最后一个出栈的。栈的结构也可以用数组或链表来实现。
下面简单实现一个基于数组结构的栈，实现只是稍微修改下上面队列结构的代码。
public class StackDemo<T> {
private Object[] object;
private int capicity;
private int size;
private final static int DEFAULT_CAPICAL = 10;
public StackDemo(){
capicity = DEFAULT_CAPICAL;
object = new Object[capicity];
}
public StackDemo(int capicity){
this.capicity = capicity;
object = new Object[this.capicity];
}
public int size(){
return size;
}
public boolean isEmpty(){
return size==0;
}
public void add(T t){
if(size == capicity){
throw new IndexOutOfBoundsException("queue is full");
}
object[size++]=t;
}
/**
* 修改移除元素的代码
*/
public void remove(){
if(isEmpty()){
throw new IndexOutOfBoundsException("queue is empty");
}
object[--size]=null;
}
public void clear(){
Arrays.fill(object, null);
size=0;
}
public void print(){
for(int i=0; i<size; i++){
System.out.println(object[i].toString());
}
}
}测试类：
public class TestStack {
/**
* @param args
*/
public static void main(String[] args) {
StackDemo<Person> queue = new StackDemo<Person>();
for(int i=0; i<10; i++){
Person p = new Person("zhang"+i, "m");
queue.add(p);
}
queue.print();
System.out.println("=====");
while(queue.size() > 0){
queue.remove();
queue.print();
System.out.println("=====");
}
}
}结果：
Person [name=zhang0, sex=m] Person [name=zhang1, sex=m] Person [name=zhang2, sex=m] Person [name=zhang3, sex=m] Person [name=zhang4, sex=m] Person [name=zhang5, sex=m] Person [name=zhang6, sex=m] Person [name=zhang7, sex=m] Person [name=zhang8, sex=m] Person [name=zhang9, sex=m] ===== Person [name=zhang0, sex=m] Person [name=zhang1, sex=m] Person [name=zhang2, sex=m] Person [name=zhang3, sex=m] Person [name=zhang4, sex=m] Person [name=zhang5, sex=m] Person [name=zhang6, sex=m] Person [name=zhang7, sex=m] Person [name=zhang8, sex=m] ===== Person [name=zhang0, sex=m] Person [name=zhang1, sex=m] Person [name=zhang2, sex=m] Person [name=zhang3, sex=m] Person [name=zhang4, sex=m] Person [name=zhang5, sex=m] Person [name=zhang6, sex=m] Person [name=zhang7, sex=m] ===== Person [name=zhang0, sex=m] Person [name=zhang1, sex=m] Person [name=zhang2, sex=m] Person [name=zhang3, sex=m] Person [name=zhang4, sex=m] Person [name=zhang5, sex=m] Person [name=zhang6, sex=m] ===== Person [name=zhang0, sex=m] Person [name=zhang1, sex=m] Person [name=zhang2, sex=m] Person [name=zhang3, sex=m] Person [name=zhang4, sex=m] Person [name=zhang5, sex=m] ===== Person [name=zhang0, sex=m] Person [name=zhang1, sex=m] Person [name=zhang2, sex=m] Person [name=zhang3, sex=m] Person [name=zhang4, sex=m] ===== Person [name=zhang0, sex=m] Person [name=zhang1, sex=m] Person [name=zhang2, sex=m] Person [name=zhang3, sex=m] ===== Person [name=zhang0, sex=m] Person [name=zhang1, sex=m] Person [name=zhang2, sex=m] ===== Person [name=zhang0, sex=m] Person [name=zhang1, sex=m] ===== Person [name=zhang0, sex=m] ===== =====
六、几种简单的线性结构介绍完了，在实际的应用环境中需要参考各种数据结构的特点来选择。
数组：查找速度很快，但长度固定，增，删效率较低。
链表：增删效率较高，长度不固定，但查找需要从头遍历整个链表，效率较低。
队列：可用数组，链表实现，先进先出。
栈：可用数组，链表实现，先进后出。