Statement stmt = conn.createStatement(ResultSet.CURSOR_SCROLL_INSENSITIVE,ResultSet.CURSOR_UPDATABLE);
ResultSet rs = stmt.executeQuery(sql);
rs.last();
int count = rs.getRow();
rs.beforeFirst();
ResultSet rs = stmt.executeQuery(sql);
rs.last();
int count = rs.getRow();
rs.beforeFirst();
sorry
说说公式解析的思路也可以!
//:Arithmetic.javapackage citi;
import java.util.Iterator;
import java.util.Stack;
import java.util.ArrayList;public class Arithmetic{
//定义操作符,为简单起见,只涉及四则运算,可相应扩充之
static String Operators="+-*/()#";
//定义操作符的比较优先级,
//其中1表示前面的操作符优于后面的操作符
// -1表示前面的操作符低于后面的操作符
// 0表示前面的操作符等于后面的操作符
// 2表示前面的操作符不可能与后面的操作符相比较,如果碰到,则表达式有错
//PrecedeList[0][]表示+和+-*/()#这七个操作符相比较的优先级
//PrecedeList[1][]表示-和+-*/()#这七个操作符相比较的优先级
//以此类推
static byte PrecedeList[][]={
{ 1, 1,-1,-1,-1, 1, 1},
{ 1, 1,-1,-1,-1, 1, 1},
{ 1, 1, 1, 1,-1, 1, 1},
{ 1, 1, 1, 1,-1, 1, 1},
{-1,-1,-1,-1,-1, 0, 2},
{ 1, 1, 1, 1, 2, 1, 1},
{-1,-1,-1,-1,-1, 2, 0}};
//定义数据中可能出现的数字和小数点,可以扩展
static String Numbers="0123456789.";
private Stack Operator,Operand;
private ArrayList Expression;
public Arithmetic(String inputStr){
Operator=new Stack();
Operator.push("#");
Operand=new Stack();
Expression=new ArrayList();
Parse(inputStr);
}
//解析输入的表达式,将操作符和数据分开
//如输入表达式2+3*(32-2)则解析成2 + 3 * ( 32 - 2 )这九个字符串
private void Parse(String instr){
String single;
int temp;
String tempstr="#";
for(int i=0;i<instr.length();i++){
single=instr.substring(i,i+1);
//排除非操作符、数字的非法输入,如2+3m
//Operators.indexOf(single)==6排除#
if(Numbers.indexOf(single)<0 && (Operators.indexOf(single)<0 || Operators.indexOf(single)==6)){
System.out.println("Input have wrong char:"+single);
Expression.clear();
return;
}
//获得前一个输入字符
temp=Expression.size()-1;
if(temp>-1){
tempstr=(String)Expression.get(temp);
}
//排除连续两个操作符的情况,如3**2
if(Operators.indexOf(single)>-1 && temp>-1 && Operators.indexOf(tempstr)>-1){
System.out.println("Input have wrong format,two Operators are conjoint");
Expression.clear();
return;
}
//如果当前字符是数字(包括.)而且前一字符也是数字,则将当前字符加到前一字符后面
//其他情况均新添加一个元素
if(Operators.indexOf(single)<0 && temp>-1 && Operators.indexOf(tempstr)<0){
Expression.set(temp,tempstr+single);
}
else{
Expression.add(single);//其他情况均新添加一个元素
}
}
//为了算法处理方便起见,添加特殊字符#
Expression.add("#");
}
//比较两个操作符的优先级
private byte Precede(String firstOperator,String secondOperator){
return PrecedeList[Operators.indexOf(firstOperator)][Operators.indexOf(secondOperator)];
}
//对两个数据字符串进行运算
private double Operate(String firstOperand,String Operator,String secondOperand){
if(Operator.equals("+")){
return (Double.parseDouble(firstOperand)+Double.parseDouble(secondOperand));
}
else if(Operator.equals("-")){
return (Double.parseDouble(firstOperand)-Double.parseDouble(secondOperand));
}
else if(Operator.equals("*")){
return (Double.parseDouble(firstOperand)*Double.parseDouble(secondOperand));
}
else if(Operator.equals("/")){
return (Double.parseDouble(firstOperand)/Double.parseDouble(secondOperand));
}
else{
System.out.println("Operator is wrong!Can throw a Exception");
return 0;
}
}
//采用两个栈对接解析后的表达式进行运算
public double Compute(){
if(Expression.isEmpty()){
System.out.println("Expresion is empty");
return 0;
}
Iterator it = Expression.iterator();
String single;
String firstOperand,secondOperand;
single=(String)it.next();
while(!(single.equals("#") && Operator.peek().equals("#"))){
if(Operators.indexOf(single)<0){
Operand.push(single);single=(String)it.next();
}
else{
switch(Precede((String)Operator.peek(),single)){
case -1:Operator.push(single);single=(String)it.next();break;
case 0: Operator.pop();single=(String)it.next();break;
case 1:
secondOperand=(String)Operand.pop();
firstOperand=(String)Operand.pop();
Operand.push(String.valueOf(Operate(firstOperand,(String)Operator.pop(),secondOperand)));break;
case 2: System.out.println("Expression is wrong!Can throw a Exception");break;
}
}
}
return Double.parseDouble((String)Operand.pop());
}
public static void main(String[] args){
long t1 = System.currentTimeMillis();
Arithmetic t=new Arithmetic(args[0]);
System.out.println(t.Compute());
long t2 = System.currentTimeMillis();
System.out.println("Time needed: " + (t2 - t1));
}
}
的算法不错,但是有点结构化语言的味道!
谁能用面向对象的思想写出来。楼主的分不够,我开帖送分
我强烈支持你的提议,不过只能声援了
谢谢 !
{
// do something...
}
支持你的提议,不过这个用javacc语法解析器来写面向对象的解析代码,还好的!我也在研究这个!呵呵
bean shell 怎么用?
// a > b
// a,b分别是字段名, number类型String code =
"\n int a = " + rs.getInt("a")
+ "\n int b = " + rs.getInt("b")
+ "\n return " + rs.getString("c");// 运行上面的java语句,返回结果并判断
if ( itp.eval(code).toString().equalsIgnoreCase("true") ) // a > b
{
}