Java example source code file (BinaryOpValueExp.java)

This example Java source code file (BinaryOpValueExp.java) is included in the alvinalexander.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" ^TM.

Learn more about this Java project at its project page.

Java - Java tags/keywords

badattributevalueexpexception, badbinaryopvalueexpexception, badstringoperationexception, binaryopvalueexp, deprecated, invalidapplicationexception, numericvalueexp, queryeval, string, stringvalueexp, valueexp

The BinaryOpValueExp.java Java example source code

/*
 * Copyright (c) 1999, 2008, Oracle and/or its affiliates. All rights reserved.
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
 *
 * This code is free software; you can redistribute it and/or modify it
 * 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.
 *
 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
 * or visit www.oracle.com if you need additional information or have any
 * questions.
 */

package javax.management;


/**
 * This class is used by the query-building mechanism to represent binary
 * operations.
 * @serial include
 *
 * @since 1.5
 */
class BinaryOpValueExp extends QueryEval implements ValueExp {

    /* Serial version */
    private static final long serialVersionUID = 1216286847881456786L;

    /**
     * @serial The operator
     */
    private int op;

    /**
     * @serial The first value
     */
    private ValueExp exp1;

    /**
     * @serial The second value
     */
    private ValueExp exp2;


    /**
     * Basic Constructor.
     */
    public BinaryOpValueExp() {
    }

    /**
     * Creates a new BinaryOpValueExp using operator o applied on v1 and
     * v2 values.
     */
    public BinaryOpValueExp(int o, ValueExp v1, ValueExp v2) {
        op   = o;
        exp1 = v1;
        exp2 = v2;
    }


    /**
     * Returns the operator of the value expression.
     */
    public int getOperator()  {
        return op;
    }

    /**
     * Returns the left value of the value expression.
     */
    public ValueExp getLeftValue()  {
        return exp1;
    }

    /**
     * Returns the right value of the value expression.
     */
    public ValueExp getRightValue()  {
        return exp2;
    }

    /**
     * Applies the BinaryOpValueExp on a MBean.
     *
     * @param name The name of the MBean on which the BinaryOpValueExp will be applied.
     *
     * @return  The ValueExp.
     *
     * @exception BadStringOperationException
     * @exception BadBinaryOpValueExpException
     * @exception BadAttributeValueExpException
     * @exception InvalidApplicationException
     */
    public ValueExp apply(ObjectName name) throws BadStringOperationException, BadBinaryOpValueExpException,
        BadAttributeValueExpException, InvalidApplicationException  {
        ValueExp val1 = exp1.apply(name);
        ValueExp val2 = exp2.apply(name);
        String sval1;
        String sval2;
        double dval1;
        double dval2;
        long   lval1;
        long   lval2;
        boolean numeric = val1 instanceof NumericValueExp;

        if (numeric) {
            if (((NumericValueExp)val1).isLong()) {
                lval1 = ((NumericValueExp)val1).longValue();
                lval2 = ((NumericValueExp)val2).longValue();

                switch (op) {
                case Query.PLUS:
                    return Query.value(lval1 + lval2);
                case Query.TIMES:
                    return Query.value(lval1 * lval2);
                case Query.MINUS:
                    return Query.value(lval1 - lval2);
                case Query.DIV:
                    return Query.value(lval1 / lval2);
                }

            } else {
                dval1 = ((NumericValueExp)val1).doubleValue();
                dval2 = ((NumericValueExp)val2).doubleValue();

                switch (op) {
                case Query.PLUS:
                    return Query.value(dval1 + dval2);
                case Query.TIMES:
                    return Query.value(dval1 * dval2);
                case Query.MINUS:
                    return Query.value(dval1 - dval2);
                case Query.DIV:
                    return Query.value(dval1 / dval2);
                }
            }
        } else {
            sval1 = ((StringValueExp)val1).getValue();
            sval2 = ((StringValueExp)val2).getValue();

            switch (op) {
            case Query.PLUS:
                return new StringValueExp(sval1 + sval2);
            default:
                throw new BadStringOperationException(opString());
            }
        }

        throw new BadBinaryOpValueExpException(this);
    }

    /**
     * Returns the string representing the object
     */
    public String toString()  {
        try {
            return parens(exp1, true) + " " + opString() + " " + parens(exp2, false);
        } catch (BadBinaryOpValueExpException ex) {
            return "invalid expression";
        }
    }

    /*
     * Add parentheses to the given subexpression if necessary to
     * preserve meaning.  Suppose this BinaryOpValueExp is
     * Query.times(Query.plus(Query.attr("A"), Query.attr("B")), Query.attr("C")).
     * Then the original toString() logic would return A + B * C.
     * We check precedences in order to return (A + B) * C, which is the
     * meaning of the ValueExp.
     *
     * We need to add parentheses if the unparenthesized expression would
     * be parsed as a different ValueExp from the original.
     * We cannot omit parentheses even when mathematically
     * the result would be equivalent, because we do not know whether the
     * numeric values will be integer or floating-point.  Addition and
     * multiplication are associative for integers but not always for
     * floating-point.
     *
     * So the rule is that we omit parentheses if the ValueExp
     * is (A op1 B) op2 C and the precedence of op1 is greater than or
     * equal to that of op2; or if the ValueExp is A op1 (B op2 C) and
     * the precedence of op2 is greater than that of op1.  (There are two
     * precedences: that of * and / is greater than that of + and -.)
     * The case of (A op1 B) op2 (C op3 D) applies each rule in turn.
     *
     * The following examples show the rules in action.  On the left,
     * the original ValueExp.  On the right, the string representation.
     *
     * (A + B) + C     A + B + C
     * (A * B) + C     A * B + C
     * (A + B) * C     (A + B) * C
     * (A * B) * C     A * B * C
     * A + (B + C)     A + (B + C)
     * A + (B * C)     A + B * C
     * A * (B + C)     A * (B + C)
     * A * (B * C)     A * (B * C)
     */
    private String parens(ValueExp subexp, boolean left)
    throws BadBinaryOpValueExpException {
        boolean omit;
        if (subexp instanceof BinaryOpValueExp) {
            int subop = ((BinaryOpValueExp) subexp).op;
            if (left)
                omit = (precedence(subop) >= precedence(op));
            else
                omit = (precedence(subop) > precedence(op));
        } else
            omit = true;

        if (omit)
            return subexp.toString();
        else
            return "(" + subexp + ")";
    }

    private int precedence(int xop) throws BadBinaryOpValueExpException {
        switch (xop) {
            case Query.PLUS: case Query.MINUS: return 0;
            case Query.TIMES: case Query.DIV: return 1;
            default:
                throw new BadBinaryOpValueExpException(this);
        }
    }

    private String opString() throws BadBinaryOpValueExpException {
        switch (op) {
        case Query.PLUS:
            return "+";
        case Query.TIMES:
            return "*";
        case Query.MINUS:
            return "-";
        case Query.DIV:
            return "/";
        }

        throw new BadBinaryOpValueExpException(this);
    }

    @Deprecated
    public void setMBeanServer(MBeanServer s) {
        super.setMBeanServer(s);
     }
 }