软件简介

Expr4J 是一个Java的表达式计算引擎，可以用来计算例如在 Excel 单元格中的表达式等。

示例代码：

package org.boris.expr.util;

import java.io.*;  
import org.boris.expr.*;  
import org.boris.expr.parser.ExprParser;

public class ExprEvaluator  
{  
    public static void main(String[] args) throws Exception {  
        SimpleEvaluationContext context = new SimpleEvaluationContext();  
        System.out.println("Expr Evaluator v1.0");  
        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));  
        while (true) {  
            try {  
                System.out.print(">");  
                String line = br.readLine();  
                if (line == null)  
                    break;  
                Expr e = ExprParser.parse(line);  
                Exprs.toUpperCase(e);  
                if (e instanceof ExprEvaluatable) {  
                    e = ((ExprEvaluatable) e).evaluate(context);  
                }  
                System.out.println(e);  
            } catch (Exception e) {  
                e.printStackTrace();  
            }  
        }  
    }  
}

package org.boris.expr.util;

import org.boris.expr.BasicEngineProvider;  
import org.boris.expr.engine.DependencyEngine;  
import org.boris.expr.engine.Range;

public class DependencyExample  
{  
    public static void main(String[] args) throws Exception {  
        DependencyEngine e = new DependencyEngine(new BasicEngineProvider());  
        e.set("B1", "=A1*2");  
        e.set("A1", "=12*2");  
        e.set("C1", "=B1*A1");  
        System.out.println(e.getValue(Range.valueOf("B1")));  
        System.out.println(e.getValue(Range.valueOf("C1")));  
        e.set("A1", "2");  
        System.out.println(e.getValue(Range.valueOf("B1")));  
        System.out.println(e.getValue(Range.valueOf("C1")));  
    }  
}