Java example source code file (BooleanExpression.java)

This example Java source code file (BooleanExpression.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

assembler, booleanexpression, conditionvars, constantexpression, context, hashtable, integer, label, object, util, vset

The BooleanExpression.java Java example source code

/*
 * Copyright (c) 1994, 2003, 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 sun.tools.tree;

import sun.tools.java.*;
import sun.tools.asm.Assembler;
import sun.tools.asm.Label;
import java.io.PrintStream;
import java.util.Hashtable;

/**
 * WARNING: The contents of this source file are not part of any
 * supported API.  Code that depends on them does so at its own risk:
 * they are subject to change or removal without notice.
 */
public
class BooleanExpression extends ConstantExpression {
    boolean value;

    /**
     * Constructor
     */
    public BooleanExpression(long where, boolean value) {
        super(BOOLEANVAL, where, Type.tBoolean);
        this.value = value;
    }

    /**
     * Get the value
     */
    public Object getValue() {
        return new Integer(value ? 1 : 0);
    }

    /**
     * Check if the expression is equal to a value
     */
    public boolean equals(boolean b) {
        return value == b;
    }


    /**
     * Check if the expression is equal to its default static value
     */
    public boolean equalsDefault() {
        return !value;
    }


    /*
     * Check a "not" expression.
     *
     * cvars is modified so that
     *    cvar.vsTrue indicates variables with a known value if
     *         the expression is true.
     *    cvars.vsFalse indicates variables with a known value if
     *         the expression is false
     *
     * For constant expressions, set the side that corresponds to our
     * already known value to vset.  Set the side that corresponds to the
     * other way to "impossible"
     */

    public void checkCondition(Environment env, Context ctx,
                               Vset vset, Hashtable exp, ConditionVars cvars) {
        if (value) {
            cvars.vsFalse = Vset.DEAD_END;
            cvars.vsTrue = vset;
        } else {
            cvars.vsFalse = vset;
            cvars.vsTrue = Vset.DEAD_END;
        }
    }


    /**
     * Code
     */
    void codeBranch(Environment env, Context ctx, Assembler asm, Label lbl, boolean whenTrue) {
        if (value == whenTrue) {
            asm.add(where, opc_goto, lbl);
        }
    }
    public void codeValue(Environment env, Context ctx, Assembler asm) {
        asm.add(where, opc_ldc, new Integer(value ? 1 : 0));
    }

    /**
     * Print
     */
    public void print(PrintStream out) {
        out.print(value ? "true" : "false");
    }
}