java如何实现抢单功能

用redis也不是不可以，但效率可能有点低，建议使用乐观锁解决这个问题。

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举个例子：

假设order表里有个version字段，该字段只能单向自增（一般就是+1），SELECT的时候把version也查出来:

SELECT ..., version FROM order WHERE ...;UPDATE orderSET ...,version = version+1WHERE version = 上一个SELECT语句带出来的version值

假设用户A和用户B在某时间段内先后或同时查出来order_id=1, version=1的订单，UPDATE的时候由于mysql行锁的存在，只会有一个用户UPDATE成功（1 rows affected），另一个用户则UPDATE失败（0 rows affected），然后可以根据UPDATE后返回的话行数判断用户是否抢单成功。

java求源代码

你是青鸟的吧 这我写过 有源码 这里怎么上传压缩包啊

package ghhh;

import java.util.Scanner;

public class DvD {

public static void main(String[] args) {

int state[]=new  int[6];

String name[]=new  String[6];

int date[]=new int[6];

int count[]=new int [6];

name[0]="权利的游戏";

name[1]="命运之夜";

name[2]="傲慢与偏见";

state[0]=1;

state[1]=0;

state[2]=1;

date[0]=13;

date[1]=0;

date[2]=9;

count[0]=23;

count[1]=23;

count[2]=23;

int n;

// boolean n=false;

do{

System.out.println("欢迎使用迷你DVD管理器");

System.out.println("1.新增DVD");

System.out.println("2.查看DVD");

System.out.println("3.删除DVD");

System.out.println("4.借出DVD");

System.out.println("5.归还DVD");

System.out.println("6.退出DVD");

Scanner input =new Scanner(System.in);

System.out.println("请选择：");

 n=input.nextInt();

switch(n){

case 1:

System.out.println("请输入要增加DVD的名称：");

String name1=input.next();

boolean flag=false;

for(int i=0;iname.length;i++){

if(name[i]==null){

name[i]=name1;

flag=true;

break;

}

}

if(flag){

System.out.println("新增DVD"+name1+"成功");

}else{

System.out.println("货架已满！增加失败！");

}

System.out.println("请输入0返回！");

n=input.nextInt();

break;

case 2:

System.out.println("序号\t"+"状态\t"+"名称\t\t"+"借出日期\t"+"借出次数");

for(int i=0;iname.length;i++){

if(name[i]!=null){

String state1 =((state[i]==0)?"可借":"已借");

String date1=((date[i]==0)?"":date[i]+"日");

String count1=count[i]+"次";

System.out.println((i+1)+"\t"+state1+"\t"+name[i]+"\t"+date1+"\t\t"+count1);

}

}

System.out.println("请输入0返回！");

n=input.nextInt();

break;

case 3:

System.out.println("请输入要删除的DVD名称：");

String name2=input.next();

int index=-1;

boolean a=false;

boolean flag1=false;

for(int i=0;iname.length;i++){

if(name2.equals(name[i])state[i]==1){

System.out.println("此DVD已经借出，无法删除");

a=true;

break;

}else if(name2.equals(name[i])state[i]==0){

a=true;

index=i;

flag1=true;

System.out.println("删除成功！");

break;

}

}

if(a==false){

System.out.println("没有找到相同名称的DVD！");

}

if(flag1){

for (int i=index;iname.length;i++){

if(i!=name.length-1){

name[i]=name[i+1];

state[i]=state[i+1];

date[i]=date[i+1];

count[i]=count[i+1];

}

name[name.length-1]=null;

state[name.length-1]=0;

date[name.length-1]=0;

count[name.length-1]=0;

}

}

System.out.println("请输入0返回！");

n=input.nextInt();

break;

case 4:

System.out.println("请输入要借出的DVD：");

 String name3=input.next();

 boolean a3=false;

 boolean b3=false;

 for(int i=0;iname.length;i++){

 if(name3.equals(name[i])  state[i]==1){

 System.out.println("该DVD已经借出");

 a3=true;

 }else if(name3.equals(name[i])  state[i]==0){

 do{

 System.out.println("请输入借出的日期：");

int m=input.nextInt();

 if(m31||m1){

 System.out.println("请重新输入日期：");

 b3=true;

 }else{

 date[i]=m; 

 state[i]=1;

 count[i]+=1;

 }

 }while(b3==true);

 System.out.println("借出成功！");

 a3=true;

 }

 }

 if(a3==false){

 System.out.println("没有该DVD");

 }

 System.out.println("请输入0返回！");

 n=input.nextInt();

break;

case 5:

System.out.println("请输入要归还的DVD：");

String name5=input.next();

boolean b5=false;

boolean m5=false;

for(int i=0;iname.length;i++){

if(name5.equals(name[i])  state[i]==1){

b5=true;

do{

System.out.println("请输入要归还DVD的日期：（归还日期请输入当月日期 1~31）");

int a5=input.nextInt();

if(a531){

System.out.println("请重新输入日期：");

m5=true;

}else if(a5date[i]){

System.out.println("借出日期是"+date[i]+"日\t输入的日期不能小于借出的日期,请重新输入日期：");

m5=true;

}else{

state[i]=0;

System.out.println("归还成功");

System.out.println("借出日期是："+date[i]+"归还日期是："+a5+"日\t租金一天一元：共"+(a5-date[i])+"元");

   date[i]=0;

   m5=false;

}

}while(m5==true);

}else if (name5.equals(name[i])  state[i]==0){

System.out.println("该DVD未借出，不可归还！");

b5=true;

}

}

if(b5==false){

System.out.println("没有该名称的DVDV");

}

System.out.println("请输入0返回！");

 n=input.nextInt();

break;

case 6:

n=1;

System.out.println("程序退出！");

break;

default:

if(n==0){

}else{

System.out.println("输入错误！请重新输入！");

n=0;

}

break;

}

}while(n==0);

System.out.println("谢谢使用！");

}

}

看看有没有问题 好久之前的了

求编写一个超级简单的Java的程序源代码

class Stack_Float

{

float nums[];

int top;

Stack_Float()

{

nums = new float[50];

top = -1;

}

boolean IsEmpty()

{

if(top == -1)

return true;

else

return false;

}

float Pop_Stack()

{

if(top==-1)

{

return 0;

}

top--;

return nums[top + 1];

}

float GetTop()

{

return nums[top];

}

void Push_Stack(float num)

{

if(top == 49)

return;

top++;

nums[top] = num;

}

}

/*****************************************************************************/

class Stack_Char

{

char str[];

int top;

Stack_Char()

{

str = new char[50];

top = -1;

}

boolean IsEmpty()

{

if(top==-1)

return true;

else

return false;

}

void Push_Stack(char ch)

{

if(top == 49)

return;

top++;

str[top] = ch;

}

char Pop_Stack()

{

if(top == -1)

return '\0';

top--;

return str[top + 1];

}

char GetTop()

{

if(top == -1)

{

System.out.print("error");

System.exit(0);

}

return str[top];

}

}

/*****************************************************************************/

public class jisuanqi extends javax.swing.JFrame

{

String show = "";

public jisuanqi()

{

initComponents();

}

char[] TranSmit(char str[])

{

char houzhui[] = new char[50]; //存放后缀表达式的字符串

int i = 0,j = 0;

char c = str[i];

Stack_Char s = new Stack_Char(); //存放运算符的栈

while(c != '=') //对算术表达式扫描未结束时

{

if(c = '0' c = '9')

{

while(c = '0' c = '9')//数字直接入栈

{

houzhui[j]=c;

j++;

i++;

c=str[i];

}

houzhui[j]='#';//用#隔开数字

j++;

}

switch(c) //扫描到运算符时

{

case '+':

case '-':

case '*':

case '/':

if(s.IsEmpty() == true) //栈空,直接入栈

{

s.Push_Stack(c);

i++;

c=str[i];

break;

}

if(ComPare(s.GetTop(),c) == -1)

{

s.Push_Stack(c); //入栈

i++;

c=str[i];

break;

}

if(ComPare(s.GetTop(),c) == 1)

{

houzhui[j]=s.Pop_Stack();//出栈元素存入后缀表达式

j++;

break;

}

}

}

while(s.IsEmpty() != true)//把剩余的运算符直接出栈

{

houzhui[j]=s.Pop_Stack();

j++;

}

houzhui[j] = '=';//后缀表达式后面加 =

j++;

houzhui[j] = '\0';

j++;

return houzhui;

}

float Count(char str[])

{

Stack_Float s = new Stack_Float();//定义存放数字的栈

char c = str[0];

int i = 0,j = 0;

float result = 0,temp,left,right;

while(c != '=') //未扫描到 = 时

{

if(c = '0' c = '9')//扫描到数字

{

temp = 0;

while(c != '#')//未读到分隔符时

{

temp = temp * 10 + c - '0';

i++;

c = str[i];

}

s.Push_Stack(temp);//进栈

}

switch(c)//扫描到运算符时

{

case '+':

{

result = s.Pop_Stack() + s.Pop_Stack();//2个数字出栈相加

s.Push_Stack(result);//最后得数进栈

break;

}

case '-':

{

right = s.Pop_Stack();//右操作数出栈

left = s.Pop_Stack();//左操作数出栈

result = left - right;

s.Push_Stack(result);

break;

}

case '*':

{

result = s.Pop_Stack() * s.Pop_Stack();//2个数字出栈相乘

s.Push_Stack(result);

break;

}

case '/':

{

right = s.Pop_Stack();//右操作数出栈

left = s.Pop_Stack();//左操作数出栈

result = left / right;

s.Push_Stack(result);

break;

}

}

i++;

c = str[i];

}

return result;

}

int ComPare(char a,char b) //判断运算符的优先级函数

{

int s[][] =

{// 栈顶元素高于算术表达式中的元素时, 返回 1,否则返回 -1

{1,1,-1,-1},

{1,1,-1,-1},

{1,1,1,1},

{1,1,1,1},

};

char x1[]={'+','-','*','/'};//栈顶元素

char x2[]={'+','-','*','/'};//算术表达式中的元素

int k=0,m,n = 0;

for(m=0;m4;m++) //查找2个进行比较的运算符在表中的位置,并返回比较结果

{

for(n=0;n4;n++)

{

if(x1[m]==ax2[n]==b)

{

k=1;break; //找到比较结果后,跳出循环

}

}

if(k==1)

break;

}

return s[m][n];//返回比较结果

}

/*****************************************************************************/

@SuppressWarnings("unchecked")

// editor-fold defaultstate="collapsed" desc="Generated Code"//GEN-BEGIN:initComponents

private void initComponents() {

text = new javax.swing.JTextField();

jButton1 = new javax.swing.JButton();

jButton2 = new javax.swing.JButton();

jButton3 = new javax.swing.JButton();

jButton4 = new javax.swing.JButton();

jButton5 = new javax.swing.JButton();

jButton6 = new javax.swing.JButton();

jButton7 = new javax.swing.JButton();

jButton8 = new javax.swing.JButton();

jButton9 = new javax.swing.JButton();

jButton10 = new javax.swing.JButton();

jButton11 = new javax.swing.JButton();

jButton12 = new javax.swing.JButton();

jButton13 = new javax.swing.JButton();

jButton14 = new javax.swing.JButton();

jButton21 = new javax.swing.JButton();

jButton22 = new javax.swing.JButton();

setDefaultCloseOperation(javax.swing.WindowConstants.EXIT_ON_CLOSE);

getContentPane().setLayout(null);

getContentPane().add(text);

text.setBounds(10, 10, 270, 30);

jButton1.setText("1");

jButton1.addActionListener(new java.awt.event.ActionListener() {

public void actionPerformed(java.awt.event.ActionEvent evt) {

jButton1ActionPerformed(evt);

}

});

getContentPane().add(jButton1);

jButton1.setBounds(10, 50, 60, 25);

jButton2.setText("2");

jButton2.addActionListener(new java.awt.event.ActionListener() {

public void actionPerformed(java.awt.event.ActionEvent evt) {

jButton2ActionPerformed(evt);

}

});

getContentPane().add(jButton2);

jButton2.setBounds(80, 50, 60, 25);

jButton3.setText("3");

jButton3.addActionListener(new java.awt.event.ActionListener() {

public void actionPerformed(java.awt.event.ActionEvent evt) {

jButton3ActionPerformed(evt);

}

});

getContentPane().add(jButton3);

jButton3.setBounds(150, 50, 60, 25);

jButton4.setText("4");

jButton4.addActionListener(new java.awt.event.ActionListener() {

public void actionPerformed(java.awt.event.ActionEvent evt) {

jButton4ActionPerformed(evt);

}

});

getContentPane().add(jButton4);

jButton4.setBounds(220, 50, 60, 25);

jButton5.setText("5");

jButton5.addActionListener(new java.awt.event.ActionListener() {

public void actionPerformed(java.awt.event.ActionEvent evt) {

jButton5ActionPerformed(evt);

}

});

getContentPane().add(jButton5);

jButton5.setBounds(10, 80, 60, 25);

jButton6.setText("6");

jButton6.addActionListener(new java.awt.event.ActionListener() {

public void actionPerformed(java.awt.event.ActionEvent evt) {

jButton6ActionPerformed(evt);

}

});

getContentPane().add(jButton6);

jButton6.setBounds(80, 80, 60, 25);

jButton7.setText("7");

jButton7.addActionListener(new java.awt.event.ActionListener() {

public void actionPerformed(java.awt.event.ActionEvent evt) {

jButton7ActionPerformed(evt);

}

});

getContentPane().add(jButton7);

jButton7.setBounds(150, 80, 60, 25);

jButton8.setText("8");

jButton8.addActionListener(new java.awt.event.ActionListener() {

public void actionPerformed(java.awt.event.ActionEvent evt) {

jButton8ActionPerformed(evt);

}

});

getContentPane().add(jButton8);

jButton8.setBounds(220, 80, 60, 25);

jButton9.setText("9");

jButton9.addActionListener(new java.awt.event.ActionListener() {

public void actionPerformed(java.awt.event.ActionEvent evt) {

jButton9ActionPerformed(evt);

}

});

getContentPane().add(jButton9);

jButton9.setBounds(10, 110, 60, 25);

jButton10.setText("0");

jButton10.addActionListener(new java.awt.event.ActionListener() {

public void actionPerformed(java.awt.event.ActionEvent evt) {

jButton10ActionPerformed(evt);

}

});

getContentPane().add(jButton10);

jButton10.setBounds(80, 110, 60, 25);

jButton11.setText("+");

jButton11.addActionListener(new java.awt.event.ActionListener() {

public void actionPerformed(java.awt.event.ActionEvent evt) {

jButton11ActionPerformed(evt);

}

});

getContentPane().add(jButton11);

jButton11.setBounds(150, 110, 60, 25);

jButton12.setText("-");

jButton12.addActionListener(new java.awt.event.ActionListener() {

public void actionPerformed(java.awt.event.ActionEvent evt) {

jButton12ActionPerformed(evt);

}

});

getContentPane().add(jButton12);

jButton12.setBounds(220, 110, 60, 25);

jButton13.setText("*");

jButton13.addActionListener(new java.awt.event.ActionListener() {

public void actionPerformed(java.awt.event.ActionEvent evt) {

jButton13ActionPerformed(evt);

}

});

getContentPane().add(jButton13);

jButton13.setBounds(10, 140, 60, 25);

jButton14.setText("/");

jButton14.addActionListener(new java.awt.event.ActionListener() {

public void actionPerformed(java.awt.event.ActionEvent evt) {

jButton14ActionPerformed(evt);

}

});

getContentPane().add(jButton14);

jButton14.setBounds(80, 140, 60, 25);

jButton21.setText("CE");

jButton21.addActionListener(new java.awt.event.ActionListener() {

public void actionPerformed(java.awt.event.ActionEvent evt) {

jButton21ActionPerformed(evt);

}

});

getContentPane().add(jButton21);

jButton21.setBounds(150, 140, 60, 25);

jButton22.setText("=");

jButton22.addActionListener(new java.awt.event.ActionListener() {

public void actionPerformed(java.awt.event.ActionEvent evt) {

jButton22ActionPerformed(evt);

}

});

getContentPane().add(jButton22);

jButton22.setBounds(220, 140, 60, 25);

pack();

}// /editor-fold//GEN-END:initComponents

private void jButton1ActionPerformed(java.awt.event.ActionEvent evt) {//GEN-FIRST:event_jButton1ActionPerformed

show += "1";

text.setText(show);

}//GEN-LAST:event_jButton1ActionPerformed

private void jButton2ActionPerformed(java.awt.event.ActionEvent evt) {//GEN-FIRST:event_jButton2ActionPerformed

show += "2";

text.setText(show);

}//GEN-LAST:event_jButton2ActionPerformed

private void jButton3ActionPerformed(java.awt.event.ActionEvent evt) {//GEN-FIRST:event_jButton3ActionPerformed

show += "3";

text.setText(show);

}//GEN-LAST:event_jButton3ActionPerformed

private void jButton4ActionPerformed(java.awt.event.ActionEvent evt) {//GEN-FIRST:event_jButton4ActionPerformed

show += "4";

text.setText(show);

}//GEN-LAST:event_jButton4ActionPerformed

private void jButton5ActionPerformed(java.awt.event.ActionEvent evt) {//GEN-FIRST:event_jButton5ActionPerformed

show += "5";

text.setText(show);

}//GEN-LAST:event_jButton5ActionPerformed

private void jButton6ActionPerformed(java.awt.event.ActionEvent evt) {//GEN-FIRST:event_jButton6ActionPerformed

show += "6";

text.setText(show);

}//GEN-LAST:event_jButton6ActionPerformed

private void jButton7ActionPerformed(java.awt.event.ActionEvent evt) {//GEN-FIRST:event_jButton7ActionPerformed

show += "7";

text.setText(show);

}//GEN-LAST:event_jButton7ActionPerformed

private void jButton8ActionPerformed(java.awt.event.ActionEvent evt) {//GEN-FIRST:event_jButton8ActionPerformed

show += "8";

text.setText(show);

}//GEN-LAST:event_jButton8ActionPerformed

private void jButton9ActionPerformed(java.awt.event.ActionEvent evt) {//GEN-FIRST:event_jButton9ActionPerformed

show += "9";

text.setText(show);

}//GEN-LAST:event_jButton9ActionPerformed

private void jButton10ActionPerformed(java.awt.event.ActionEvent evt) {//GEN-FIRST:event_jButton10ActionPerformed

show += "0";

text.setText(show);

}//GEN-LAST:event_jButton10ActionPerformed

private void jButton13ActionPerformed(java.awt.event.ActionEvent evt) {//GEN-FIRST:event_jButton13ActionPerformed

show += "*";

text.setText(show);

}//GEN-LAST:event_jButton13ActionPerformed

private void jButton14ActionPerformed(java.awt.event.ActionEvent evt) {//GEN-FIRST:event_jButton14ActionPerformed

show += "/";

text.setText(show);

}//GEN-LAST:event_jButton14ActionPerformed

private void jButton21ActionPerformed(java.awt.event.ActionEvent evt) {//GEN-FIRST:event_jButton21ActionPerformed

show = "";

text.setText("");

}//GEN-LAST:event_jButton21ActionPerformed

private void jButton22ActionPerformed(java.awt.event.ActionEvent evt) {//GEN-FIRST:event_jButton22ActionPerformed

show += "=";

text.setText(show);

char str1[] = new char[50];

char str2[] = new char[50];

float result = 0;

str1 = show.toCharArray();

str2 = TranSmit(str1);

result = Count(str2);

text.setText("" + result);

show = "";

}//GEN-LAST:event_jButton22ActionPerformed

private void jButton12ActionPerformed(java.awt.event.ActionEvent evt) {//GEN-FIRST:event_jButton12ActionPerformed

show += "-";

text.setText(show);

}//GEN-LAST:event_jButton12ActionPerformed

private void jButton11ActionPerformed(java.awt.event.ActionEvent evt) {//GEN-FIRST:event_jButton11ActionPerformed

show += "+";

text.setText(show);

}//GEN-LAST:event_jButton11ActionPerformed

public static void main(String args[])

{

jisuanqi j = new jisuanqi();

j.setBounds(300, 300, 300, 195);

j.setVisible(true);

}

// Variables declaration - do not modify//GEN-BEGIN:variables

private javax.swing.JButton jButton1;

private javax.swing.JButton jButton10;

private javax.swing.JButton jButton11;

private javax.swing.JButton jButton12;

private javax.swing.JButton jButton13;

private javax.swing.JButton jButton14;

private javax.swing.JButton jButton2;

private javax.swing.JButton jButton21;

private javax.swing.JButton jButton22;

private javax.swing.JButton jButton3;

private javax.swing.JButton jButton4;

private javax.swing.JButton jButton5;

private javax.swing.JButton jButton6;

private javax.swing.JButton jButton7;

private javax.swing.JButton jButton8;

private javax.swing.JButton jButton9;

private javax.swing.JTextField text;

// End of variables declaration//GEN-END:variables

}