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Groovy example source code file (

This example Groovy source code file ( is included in the "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 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
 * 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="">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);

Other Groovy examples (source code examples)

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