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POLong to Double in Jexl
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  1. POLong to Double in Jexl
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    copied!<p>I use Jexl lib from apache and have some problems with using the <code>evaluate()</code> method of Expression class. Here is the code of NelderMead class:</p> <pre><code>import org.apache.commons.jexl2.*; public class NelderMead { // контсанты private static int M = 3; private static double E = 0.005; private static double A = 1.000; private static double B = 0.500; private static double Y = 2.000; // переменные private JexlEngine jexl; private Expression func; private String funcString = ""; private MapContext[] iterations; public NelderMead(){ this.jexl = new JexlEngine(); } public NelderMead(String funcString){ this.jexl = new JexlEngine(); this.setFunc(funcString); } public void setFunc(String funcString){ this.funcString = funcString; this.func = this.jexl.createExpression(funcString); } public double funcEval(MapContext args){ return ((Double) this.func.evaluate(args)).doubleValue(); } public boolean checkCriterian(){ return true; } } </code></pre> <p>And the code of testcase is:</p> <pre><code>import org.apache.commons.jexl2.MapContext; public class Test { /** * @param args */ public static void main(String[] args) { NelderMead nm = new NelderMead("(x1-2)^4+(x1-2*x2)^2"); MapContext mc = new MapContext(); mc.set("x1", 2); mc.set("x2", 1); System.out.println(nm.funcEval(mc)); } } </code></pre> <p>And when I run the testcase, it cause the following error:</p> <pre><code>Exception in thread "main" java.lang.ClassCastException: java.lang.Long cannot be cast to java.lang.Double at NelderMead.funcEval(NelderMead.java:33) at Test.main(Test.java:14) </code></pre> <p>I can't understand why it can't cast to Double?</p> <p>PS</p> <p><a href="http://commons.apache.org/jexl/apidocs/org/apache/commons/jexl2/Expression.html#evaluate%28org.apache.commons.jexl2.JexlContext%29" rel="nofollow">Here</a> is the javadoc of evaluate() function.</p>
 

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