constantexpression.java

大名鼎鼎的java动态脚本语言。已经通过了sun的认证

/*
 $Id: ConstantExpression.java,v 1.11 2005/12/14 16:51:43 blackdrag Exp $

 Copyright 2003 (C) James Strachan and Bob Mcwhirter. All Rights Reserved.

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 ("Software"), with or without modification, are permitted provided
 that the following conditions are met:

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    statements and notices.  Redistributions must also contain a
    copy of this document.

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    products derived from this Software without prior written
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    please contact [e-mail].

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    trademark of The Codehaus.

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    http://groovy.codehaus.org/

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 ``AS IS'' AND ANY EXPRESSED OR IMPLIED WARRANTIES, INCLUDING, BUT
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 */
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:[e-mail]">James Strachan</a>
 * @version $Revision: 1.11 $
 */
public class ConstantExpression extends Expression {
    public static final ConstantExpression VOID = new ConstantExpression(Void.class);
    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 Expression EMPTY_ARRAY = new PropertyExpression(new ClassExpression(ArgumentListExpression.class.getName()), "EMPTY_ARRAY");
    public static final ConstantExpression EMTPY_EXPRESSION = new ConstantExpression(null);
    
    private Object value;
    
    public ConstantExpression(Object value) {
        this.value = value;
        if (this.value != null)
            setType(ClassHelper.make(value.getClass()));
    }

    public String toString() {
        return super.toString() +"[value=" + value + "]";
    }

    public void visit(GroovyCodeVisitor visitor) {
        visitor.visitConstantExpression(this);
    }


    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();
    }
}