Java数学表达式计算(Expression Evaluator)

常见的表达式计算lib有：

• parsii
• JEval
• JEPLite
• expr
• Janino
• MathEval

(1)parsii

String exp = "2 + (7-5) * 3.14159 * x + sin(0)";

// compile
Scope scope = Scope.create();
Expression parsiiExpr = Parser.parse(exp);
Variable var = scope.getVariable("x");
var.setValue(X_VALUE);

// evaluate
double result = parsiiExpr.evaluate();

System.out.println(result);//-> 2.0

(2)JEval

String exp = "2 + (7-5) * 3.14159 * #{x} + sin(0)";

// compile
Evaluator jevalEvaluator = new Evaluator();
jevalEvaluator.setVariables(Collections.singletonMap("x", Double.toString(X_VALUE)));

// evaluate
double result = Double.parseDouble(jevalEvaluator.evaluate(exp));

System.out.println(result);//-> 2.0

(3)JEPLite

String exp = "2 + (7-5) * 3.14159 * x + sin(0)";

// compile
JEP jep = new JEP();
jep.addVariable("x", X_VALUE);
jep.parseExpression(exp);
DoubleStack jepStack = new DoubleStack();

// evaluate
double result = jep.getValue(jepStack);

System.out.println(result);//-> 2.0

http://andreas.haufler.info/2013/12/how-to-write-one-of-fastest-expression.html
http://www.transylvania-jug.org/archives/5777