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Groovy example source code file (ConstantExpression.java)

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

Java - Groovy tags/keywords

boolean, constantexpression, constantexpression, empty_expression, expression, expression, object, object, prim_false, prim_true, string, string, true, void

The Groovy ConstantExpression.java source code

 * Copyright 2003-2007 the original author or authors.
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *     http://www.apache.org/licenses/LICENSE-2.0
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * See the License for the specific language governing permissions and
 * limitations under the License.
package org.codehaus.groovy.ast.expr;

import org.codehaus.groovy.ast.ClassHelper;
import org.codehaus.groovy.ast.GroovyCodeVisitor;

 * Represents a constant expression such as null, true, false
 * @author <a href="mailto:james@coredevelopers.net">James Strachan
 * @version $Revision: 21186 $
public class ConstantExpression extends Expression {
    // The following fields are only used internally; every occurrence of a user-defined expression of the same kind
    // has its own instance so as to preserve line information. Consequently, to test for such an expression, don't
    // compare against the field but call isXXXExpression() instead.
    public static final ConstantExpression NULL = new ConstantExpression(null);
    public static final ConstantExpression TRUE = new ConstantExpression(Boolean.TRUE);
    public static final ConstantExpression FALSE = new ConstantExpression(Boolean.FALSE);
    public static final ConstantExpression EMPTY_STRING = new ConstantExpression("");
    public static final ConstantExpression PRIM_TRUE = new ConstantExpression(Boolean.TRUE, true);
    public static final ConstantExpression PRIM_FALSE = new ConstantExpression(Boolean.FALSE, true);
    //public static final Expression EMPTY_ARRAY = new PropertyExpression(new ClassExpression(ArgumentListExpression.class.getName()), "EMPTY_ARRAY");

    // the following fields are only used internally; there are no user-defined expressions of the same kind
    public static final ConstantExpression VOID = new ConstantExpression(Void.class);
    public static final ConstantExpression EMPTY_EXPRESSION = new ConstantExpression(null);
    private Object value;
    private String constantName;

    public ConstantExpression(Object value) {

    public ConstantExpression(Object value, boolean keepPrimitive) {
        this.value = value;
        if (value != null) {
            if (keepPrimitive) {
                if (value instanceof Integer) {
                } else if (value instanceof Boolean) {
                } else {
                //TODO: more cases here
            } else {

    public String toString() {
        return "ConstantExpression[" + value + "]";

    public void visit(GroovyCodeVisitor visitor) {

    public Expression transformExpression(ExpressionTransformer transformer) {
        return this;

     * @return the value of this constant expression
    public Object getValue() {
        return value;

    public String getText() {
        return (value == null) ? "null" : value.toString();

    public String getConstantName() {
        return constantName;

    public void setConstantName(String constantName) {
        this.constantName = constantName;

    public boolean isNullExpression() {
        return value == null;

    public boolean isTrueExpression() {
        return Boolean.TRUE.equals(value);

    public boolean isFalseExpression() {
        return Boolean.FALSE.equals(value);

    public boolean isEmptyStringExpression() {
        return "".equals(value);

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