/*
* Copyright (c) 2004, Oracle and/or its affiliates. All rights reserved.
* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
*
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* under the terms of the GNU General Public License version 2 only, as
* published by the Free Software Foundation. Oracle designates this
* particular file as subject to the "Classpath" exception as provided
* by Oracle in the LICENSE file that accompanied this code.
*
* This code is distributed in the hope that it will be useful, but WITHOUT
* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
* version 2 for more details (a copy is included in the LICENSE file that
* accompanied this code).
*
* You should have received a copy of the GNU General Public License version
* 2 along with this work; if not, write to the Free Software Foundation,
* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
*
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package sun.tools.jstat;
import java.util.*;
import sun.jvmstat.monitor.*;
/**
* A class implementing the ExpressionEvaluator to evaluate an expression
* in the context of the available monitoring data.
*
* @author Brian Doherty
* @since 1.5
*/
public class ExpressionExecuter implements ExpressionEvaluator {
private static final boolean debug =
Boolean.getBoolean("ExpressionEvaluator.debug");
private MonitoredVm vm;
private HashMap<String, Object> map = new HashMap<String, Object>();
ExpressionExecuter(MonitoredVm vm) {
this.vm = vm;
}
/*
* evaluate the given expression.
*/
public Object evaluate(Expression e) {
if (e == null) {
return null;
}
if (debug) {
System.out.println("Evaluating expression: " + e);
}
if (e instanceof Literal) {
return ((Literal)e).getValue();
}
if (e instanceof Identifier) {
Identifier id = (Identifier)e;
if (map.containsKey(id.getName())) {
return map.get(id.getName());
} else {
// cache the data values for coherency of the values over
// the life of this expression executer.
Monitor m = (Monitor)id.getValue();
Object v = m.getValue();
map.put(id.getName(), v);
return v;
}
}
Expression l = e.getLeft();
Expression r = e.getRight();
Operator op = e.getOperator();
if (op == null) {
return evaluate(l);
} else {
Double lval = new Double(((Number)evaluate(l)).doubleValue());
Double rval = new Double(((Number)evaluate(r)).doubleValue());
double result = op.eval(lval.doubleValue(), rval.doubleValue());
if (debug) {
System.out.println("Performed Operation: " + lval + op + rval
+ " = " + result);
}
return new Double(result);
}
}
}