https://openjdk.java.net/ 
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 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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 * 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
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 *
 * 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).
 *
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 * 2 along with this work; if not, write to the Free Software Foundation,
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 *
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package com.sun.codemodel.internal.fmt;

import java.io.BufferedReader;
import java.io.BufferedWriter;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.OutputStream;
import java.io.OutputStreamWriter;
import java.io.PrintWriter;
import java.text.ParseException;
import java.util.Iterator;
import java.util.List;

import com.sun.codemodel.internal.JClass;
import com.sun.codemodel.internal.JPackage;
import com.sun.codemodel.internal.JResourceFile;
import com.sun.codemodel.internal.JTypeVar;


Statically generated Java soruce file.

 This JResourceFile implementation will generate a Java source file by copying the source code from a resource. 

While copying a resource, we look for a package declaration and
replace it with the target package name. This allows the static Java
source code to have an arbitrary package declaration.

 You can also use the getJClass method to obtain a JClass object that represents the static file. This allows the client code to refer to the class from other CodeModel generated code. 
 Note that because we don't parse the static Java source code, the returned JClass object doesn't respond to methods like "isInterface" or "_extends", 
Author:
    Kohsuke Kawaguchi (kohsuke.kawaguchi@sun.com)
/**
 * Statically generated Java soruce file.
 *
 * <p>
 * This {@link JResourceFile} implementation will generate a Java source
 * file by copying the source code from a resource.
 * <p>
 * While copying a resource, we look for a package declaration and
 * replace it with the target package name. This allows the static Java
 * source code to have an arbitrary package declaration.
 * <p>
 * You can also use the getJClass method to obtain a {@link JClass}
 * object that represents the static file. This allows the client code
 * to refer to the class from other CodeModel generated code.
 * <p>
 * Note that because we don't parse the static Java source code,
 * the returned {@link JClass} object doesn't respond to methods like
 * "isInterface" or "_extends",
 *
 * @author
 *     Kohsuke Kawaguchi (kohsuke.kawaguchi@sun.com)
 */
public final class JStaticJavaFile extends JResourceFile {

    private final JPackage pkg;
    private final String className;
    private final ResourceLoader source;
    private final JStaticClass clazz;
    private final LineFilter filter;

    public JStaticJavaFile(JPackage _pkg, String _className, Class<?> loadingClass, LineFilter _filter) {
        super(_className + ".java");
        if (loadingClass == null) throw new NullPointerException();
        this.pkg = _pkg;
        this.clazz = new JStaticClass();
        this.className = _className;
        this.source = new ResourceLoader(_className, loadingClass);
        this.filter = _filter;
    }

    
Returns a class object that represents a statically generated code.

/**
     * Returns a class object that represents a statically generated code.
     */
    public final JClass getJClass() {
        return clazz;
    }

    protected boolean isResource() {
        return false;
    }

    protected  void build(OutputStream os) throws IOException {
        int lineNumber=1;
        try (
                InputStream is = source.getResourceAsStream();
                BufferedReader r = new BufferedReader(new InputStreamReader(is));
                PrintWriter w = new PrintWriter(new BufferedWriter(new OutputStreamWriter(os)));
        ) {
            LineFilter filter = createLineFilter();
            String line;
            while((line=r.readLine())!=null) {
                line = filter.process(line);
                if(line!=null)
                    w.println(line);
                lineNumber++;
            }
        } catch( ParseException e ) {
            throw new IOException("unable to process "+source+" line:"+lineNumber+"\n"+e.getMessage());
        }
    }

    
Creates a LineFilter. 

A derived class can override this method to process
the contents of the source file.

/**
     * Creates a {@link LineFilter}.
     * <p>
     * A derived class can override this method to process
     * the contents of the source file.
     */
    private LineFilter createLineFilter() {
        // this filter replaces the package declaration.
        LineFilter f = new LineFilter() {
            public String process(String line) {
                if(!line.startsWith("package ")) return line;

                // replace package decl
                if( pkg.isUnnamed() )
                    return null;
                else
                    return "package "+pkg.name()+";";
            }
        };
        if( filter!=null )
            return new ChainFilter(filter,f);
        else
            return f;
    }

    
Filter that alters the Java source code.


By implementing this interface, derived classes
can modify the Java source file before it's written out.

/**
     * Filter that alters the Java source code.
     * <p>
     * By implementing this interface, derived classes
     * can modify the Java source file before it's written out.
     */
    public interface LineFilter {
        
Params:
  • line – 
     a non-null valid String that corresponds to one line.
     No '\n' included.
Throws:
Returns:
     null to strip the line off. Otherwise the returned
     String will be written out. Do not add '\n' at the end
     of this string.
/**
         * @param line
         *      a non-null valid String that corresponds to one line.
         *      No '\n' included.
         * @return
         *      null to strip the line off. Otherwise the returned
         *      String will be written out. Do not add '\n' at the end
         *      of this string.
         *
         * @exception ParseException
         *      when for some reason there's an error in the line.
         */
        String process(String line) throws ParseException;
    }

    
A LineFilter that combines two LineFilters. 
/**
     * A {@link LineFilter} that combines two {@link LineFilter}s.
     */
    public final static class ChainFilter implements LineFilter {
        private final LineFilter first,second;
        public ChainFilter( LineFilter first, LineFilter second ) {
            this.first=first;
            this.second=second;
        }
        public String process(String line) throws ParseException {
            line = first.process(line);
            if(line==null)  return null;
            return second.process(line);
        }
    }


    private class JStaticClass extends JClass {

        private final JTypeVar[] typeParams;

        JStaticClass() {
            super(pkg.owner());
            // TODO: allow those to be specified
            typeParams = new JTypeVar[0];
        }

        public String name() {
            return className;
        }

        public String fullName() {
            if(pkg.isUnnamed())
                return className;
            else
                return pkg.name()+'.'+className;
        }

        public JPackage _package() {
            return pkg;
        }

        public JClass _extends() {
            throw new UnsupportedOperationException();
        }

        public Iterator<JClass> _implements() {
            throw new UnsupportedOperationException();
        }

        public boolean isInterface() {
            throw new UnsupportedOperationException();
        }

        public boolean isAbstract() {
            throw new UnsupportedOperationException();
        }

        public JTypeVar[] typeParams() {
            return typeParams;
        }

        protected JClass substituteParams(JTypeVar[] variables, List<JClass> bindings) {
            return this;
        }
    }

    static class ResourceLoader {
        Class<?> loadingClass;
        String shortName;

        ResourceLoader(String shortName, Class<?> loadingClass) {
            this.loadingClass = loadingClass;
            this.shortName = shortName;
        }

        InputStream getResourceAsStream() {
            // some people didn't like our jars to contain files with .java extension,
            // so when we build jars, we'' use ".java_". But when we run from the workspace,
            // we want the original source code to be used, so we check both here.
            // see bug 6211503.
            InputStream stream = loadingClass.getResourceAsStream(shortName + ".java");
            if (stream == null) {
                stream = loadingClass.getResourceAsStream(shortName + ".java_");
            }
            if (stream == null) {
                throw new InternalError("Unable to load source code of " + loadingClass.getName() + " as a resource");
            }
            return stream;
        }

    }

}