这篇文章主要为大家展示了“JAVA中如何实现表达式计算源码”，内容简而易懂，条理清晰，希望能够帮助大家解决疑惑，下面让小编带领大家一起研究并学习一下“JAVA中如何实现表达式计算源码”这篇文章吧。
支持运算符：+-*/%><][!|&=；其中]表示大于等于、[表示小于等于、！表示不等于、｜表示或、＆表示与、＝表示是否等于
支持函数：sqrt,square, ceil,sin,cos,asin,acon.tan.atan,log,exp具体含义见calFunction代码
表达式计算组件源码：
import Java.util.Stack;
import java.util.regex.*;
public class BaseExpression {
public static String OPTS = "+-*/%><][!|&=# public="" object="" string="" throws="" stack="" opts="new" values="new" exp="expression" int="" ncount="exp.length()," temp="this.getValue(temp);<BR" optout="" optin="Opts.pop().toString();<BR" value1="Values.pop().toString();<BR" value2="Values.pop().toString();<BR" opttemp="" opt="exp.substring(i" temp1="" nfun="" boolean="" isfun="true;<BR" for="" i="i" ntemp="" while="" if="" else="" -="" nin="" nout="this.getOptPriorityOut(temp);<BR" ret="String.valueOf(this.calValue(value2," return="" expressionexception="" throw="" exception="" new="" expression="" protected="">")) {
return 11;
}
else if (opt.equals("<")) {
return 12;
}
else if (opt.equals("]")) {
return 13;
}
else if (opt.equals("[")) {
return 14;
}
else if (opt.equals("!")) {
return 15;
}
else if (opt.equals("|")) {
return 16;
}
else if (opt.equals("&") )
{
return 23;
}
else if (opt.equals("=") )
{
return 25;
}
else if ( opt.equals("#"))
{
return 0;
}
else if (opt.equals("(")) {
return 1000;
}
else if (opt.equals(")")) {
return -1000;
}
throw new ExpressionException("运算符" + opt + "非法!");
}
protected int getOptPriorityIn(String opt) throws ExpressionException{
if (opt.equals("+")) {
return 3;
}
else if (opt.equals("-")) {
return 4;
}
else if (opt.equals("*")) {
return 8;
}
else if (opt.equals("/")) {
return 9;
}
else if (opt.equals("%")) {
return 10;
}
else if (opt.equals(">")) {
return 17;
}
else if (opt.equals("<")) {
return 18;
}
else if (opt.equals("]")) {
return 19;
}
else if (opt.equals("[")) {
return 20;
}
else if (opt.equals("!")) {
return 21;
}
else if (opt.equals("|")) {
return 22;
}
else if( opt.equals("&") )
{
return 24;
}
else if( opt.equals("=") )
{
return 26;
}
else if (opt.equals("(")) {
return -1000;
}
else if (opt.equals(")")) {
return 1000;
}
else if (opt.equals("#")) {
return 0;
}
throw new ExpressionException("运算符" + opt + "非法！");
}
protected String getOPTS()
{
return OPTS;
}
protected boolean isValue(String cValue) {
String notValue = this.getOPTS() + "()";
return notValue.indexOf(cValue) == -1;
}
protected boolean isOpt(String value) {
return this.getOPTS().indexOf(value) >= 0;
}
protected double calValue(String value1, String opt, String value2) throws ExpressionException{
try
{
double dbValue1 = Double.valueOf(value1).doubleValue();
double dbValue2 = Double.valueOf(value2).doubleValue();
long lg = 0;
if (opt.equals("+")) {
return dbValue1 + dbValue2;
}
else if (opt.equals("-")) {
return dbValue1 - dbValue2;
}
else if (opt.equals("*")) {
return dbValue1 * dbValue2;
}
else if (opt.equals("/")) {
return dbValue1 / dbValue2;
}
else if (opt.equals("%")) {
lg = (long) (dbValue1 / dbValue2);
return dbValue1 - lg * dbValue2;
}
else if (opt.equals(">")) {
if (dbValue1 > dbValue2)
return 1;
else
return 0;
}
else if (opt.equals("<")) {
if (dbValue1 < dbValue2)
return 1;
else
return 0;
}
else if (opt.equals("]")) {
if (dbValue1 >= dbValue2)
return 1;
else
return 0;
}
else if (opt.equals("[")) {
if (dbValue1 <= dbValue2)
return 1;
else
return 0;
}
else if (opt.equals("!")) {
if (dbValue1 != dbValue2)
return 1;
else
return 0;
}
else if (opt.equals("|")) {
if (dbValue1 > 0 || dbValue2 > 0)
return 1;
else
return 0;
}
else if (opt.equals("&")) {
if (dbValue1 > 0 && dbValue2 > 0)
return 1;
else
return 0;
}
else if (opt.equals("=")) {
if (dbValue1 == dbValue2)
return 1;
else
return 0;
}
}catch(Exception e)
{
throw new ExpressionException("值" + value1 + "或" + value2 + "在进行" + opt + "运算时非法！");
}
throw new ExpressionException("运算符" + opt + "非法！");
}
protected String getValue(String oldValue) throws ExpressionException{
String reg = "^([a-zA-Z0-9_]+)(([a-zA-Z0-9_.()]+))$";
if (this.isFunctionCal(oldValue)) {
Pattern p = Pattern.compile(reg);
Matcher m = p.matcher(oldValue);
m.find();
return calFunction(m.group(1), m.group(2));
}
return oldValue;
}
protected boolean isFunctionCal(String value) {
String reg = "^([a-zA-Z0-9_]+)(([a-zA-Z0-9_.()]+))$";
return value.matches(reg);
}
protected String calFunction(String function, String value) throws ExpressionException{
String lowerFun = function.toLowerCase();
double db = 0;
try
{
db = Double.valueOf(this.getValue(value)).doubleValue();
if (lowerFun.equals("log")) {
return String.valueOf(Math.log(db));
}
else if (lowerFun.equals("square")) {
return String.valueOf(Math.pow(db, 2));
}
else if (lowerFun.equals("sqrt")) {
return String.valueOf(Math.sqrt(db));
}
else if (lowerFun.equals("sin")) {
return String.valueOf(Math.sin(db));
}
else if (lowerFun.equals("asin")) {
return String.valueOf(Math.asin(db));
}
else if (lowerFun.equals("cos")) {
return String.valueOf(Math.cos(db));
}
else if (lowerFun.equals("tan")) {
return String.valueOf(Math.tan(db));
}
else if (lowerFun.equals("atan")) {
return String.valueOf(Math.atan(db));
}
else if (lowerFun.equals("ceil")) {
return String.valueOf(Math.ceil(db));
}
else if (lowerFun.equals("exp")) {
return String.valueOf(Math.exp(db));
}
}catch(Exception e)
{
throw new ExpressionException("函数" + function + "值" + value + "非法!");
}
throw new ExpressionException("函数" + function + "不支持！");
}
public static void main(String[] args)
{
BaseExpression be = new BaseExpression();
String exp = "sin(ceil(sqrt(100)))*29+20+30*3+0|0|1+1&1*5+2=2";
try
{
System.out.println(be.calculate(exp));
}
catch(ExpressionException eE)
{
System.out.println(eE.getMessage());
}
}
}
表达式异常类代码：
public class ExpressionException extends Exception{
public ExpressionException(String msg)
{
super(msg);
}
}
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