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Scala example source code file (JClass.java)

This example Scala source code file (JClass.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 - Scala tags/keywords

dataoutputstream, io, ioexception, ioexception, iterator, jclass, jfield, jfield, jinnerclassesattribute, jinnerclassesattribute, jmethod, jtype, string, string, stringbuffer, util

The Scala JClass.java source code

/* FJBG -- Fast Java Bytecode Generator
 * Copyright 2002-2011 LAMP/EPFL
 * @author  Michel Schinz
 */

package ch.epfl.lamp.fjbg;

import java.util.*;
import java.io.*;

/**
 * Representation of a Java class.
 *
 * @author Michel Schinz, Stephane Micheloud
 * @version 1.1
 */
public class JClass extends JMember {

    /** Magic number for Java class files. */
    public final static int MAGIC_NUMBER = 0xCAFEBABE;

    protected final JAttributeFactory attributeFactory;

    protected final String superclassName;
    protected final String[] interfaceNames;
    protected final String sourceFileName;
    protected final JConstantPool pool;

    protected JBootstrapInvokeDynamic bootstrapClassAttr = null;

    public final static String[] NO_INTERFACES = new String[0];

    protected final LinkedList/*<JMethod>*/ methods = new LinkedList();
    protected final LinkedList/*<JField>*/ fields = new LinkedList();

    protected JInnerClassesAttribute innerClasses;

    protected int major;
    protected int minor;

    /**
     * Creates a new class with its access flags, name, superclass name,
     * interfaces names and source file name initialized to a given value.
     * The constructor also initializes the pool and adds a sourceFileName
     * attribute to the class.
     * @param accessFlags the int representing the access flags of the class.
     * @param name the string representing the name of the class.
     * @param superclassName the string representing the name of the class'
     * superclass.
     * @param interfaceNames the list of strings representing the names of the
     * interfaces implemented by the class.
     * @param sourceFileName name of the file from which the class was compiled.
     */
    protected JClass(FJBGContext context,
                     int accessFlags,
                     String name,
                     String superclassName,
                     String[] interfaceNames,
                     String sourceFileName) {
        super(context, accessFlags, name);
        this.attributeFactory = context.getJAttributeFactory();

        this.major = context.MAJOR_VERSION;
        this.minor = context.MINOR_VERSION;

        this.superclassName = superclassName;
        this.interfaceNames = interfaceNames;
        this.sourceFileName = sourceFileName;
        this.pool = context.JConstantPool();
        if (sourceFileName != null)
            addAttribute(context.JSourceFileAttribute(this, sourceFileName));
    }

    protected JClass(FJBGContext context, DataInputStream stream)
        throws IOException {
        super(context);
        this.attributeFactory = context.getJAttributeFactory();

        int magic = stream.readInt();
        if (magic != MAGIC_NUMBER)
            throw new IllegalArgumentException("invalid magic number: "+magic);

        minor = stream.readShort();
        major = stream.readShort();
        pool = context.JConstantPool(stream);
        accessFlags = stream.readShort();

        // This class, super class and interfaces
        name = pool.lookupClass(stream.readShort());
        superclassName = pool.lookupClass(stream.readShort());
        interfaceNames = new String[stream.readShort()];
        for (int i = 0; i < interfaceNames.length; ++i)
            interfaceNames[i] = pool.lookupClass(stream.readShort());

        // Fields, methods and attributes
        int fieldsCount = stream.readShort();
        for (int i = 0; i < fieldsCount; ++i)
            addField(context.JField(this, stream));

        int methodsCount = stream.readShort();
        for (int i = 0; i < methodsCount; ++i)
            addMethod(context.JMethod(this, stream));

        String fileName = null;
        int attributesCount = stream.readShort();
        for (int i = 0; i < attributesCount; ++i) {
            JAttribute attr = attributeFactory.newInstance(this, this, stream);
            if (attr instanceof JSourceFileAttribute)
                fileName = ((JSourceFileAttribute)attr).getFileName();
            else if (attr instanceof JInnerClassesAttribute)
                innerClasses = (JInnerClassesAttribute)attr;
            addAttribute(attr);
        }
        sourceFileName = fileName;
    }

    /**
     * Gets the name of the class' superclass.
     * @return The string representing the name of the class' superclass.
     */
    public String getSuperclassName() { return superclassName; }

    /**
     * Gets the names of the interfaces implemented by the class.
     * @return The array containing the string representations of the
     * names of the interfaces implemented by the class.
     */
    public String[] getInterfaceNames() { return interfaceNames; }

    /**
     * Gets the source file name of this class.
     * @return The string representing the source file name of this class.
     */
    public String getSourceFileName() { return sourceFileName; }

    /**
     * Gets the type of the objects that are instances of the class.
     * @return The type of the instances of the class.
     */
    public JType getType() { return new JObjectType(name); }

    public JClass getJClass() { return this; }

    public boolean isPublic() {
        return (accessFlags & JAccessFlags.ACC_PUBLIC) != 0;
    }

    public boolean isPrivate() {
        return (accessFlags & JAccessFlags.ACC_PRIVATE) != 0;
    }

    public boolean isProtected() {
        return (accessFlags & JAccessFlags.ACC_PROTECTED) != 0;
    }

    public boolean isStatic() {
        return (accessFlags & JAccessFlags.ACC_STATIC) != 0;
    }

    public boolean isFinal() {
        return (accessFlags & JAccessFlags.ACC_FINAL) != 0;
    }

    public boolean isAbstract() {
        return (accessFlags & JAccessFlags.ACC_ABSTRACT) != 0;
    }

    /**
     * Gets the version number of the class.
     * @param major The int representing the major part of the version number
     * of the class.
     * @param minor The int representing the minor part of the version number
     * of the class.
     */
    public void setVersion(int major, int minor) {
        assert !frozen;
        this.major = major;
        this.minor = minor;
    }

    /**
     * Gets the major part of the number describing the version of the class.
     * @return The int representing the major part of the version number of
     * the class.
     */
    public int getMajorVersion() { return major; }

    /**
     * Gets the minor part of the number describing the version of the class.
     * @return The int representing the minor part of the version number of
     * the class.
     */
    public int getMinorVersion() { return minor; }

    /**
     * Gets the constant pool of the class.
     * @return The constant pool of the class.
     */
    public JConstantPool getConstantPool() { return pool; }

    public JInnerClassesAttribute getInnerClasses() {
    	if (innerClasses == null) {
    		innerClasses = new JInnerClassesAttribute(context, this);
    		addAttribute(innerClasses);
    	}
    	return innerClasses;
    }
    
    /**
     * Decides if the class is an interface.
     * @return The boolean representing if the class is an interface or not.
     */
    public boolean isInterface() {
        return (accessFlags & JAccessFlags.ACC_INTERFACE) != 0;
    }

    public void addField(JField field) {
        assert !frozen;
        fields.add(field);
    }

    /**
     * Create and add a new field to the class.
     */
    public JField addNewField(int accessFlags, String name, JType type) {
        assert !frozen;
        JField f = context.JField(this, accessFlags, name, type);
        addField(f);
        return f;
    }

    protected void addMethod(JMethod method) {
        assert !frozen;
        methods.add(method);
    }

    /**
     * Create and add a new method to the class.
     */
    public JMethod addNewMethod(int accessFlags,
                                String name,
                                JType returnType,
                                JType[] argTypes,
                                String[] argNames) {
        assert !frozen;
        JMethod m = context.JMethod(this,
                                    accessFlags,
                                    name,
                                    returnType,
                                    argTypes,
                                    argNames);
        addMethod(m);
        return m;
    }

    /**
     * Remove a previously-added method. This makes no attempt at
     * minimising the constant pool by removing all constants which
     * were used only by this method.
     */
    public void removeMethod(JMethod m) {
        assert !frozen;
        methods.remove(m);
    }

    public JField[] getFields() {
        return (JField[])fields.toArray(new JField[fields.size()]);
    }

    public JMethod[] getMethods() {
        return (JMethod[])methods.toArray(new JMethod[methods.size()]);
    }

    /**
     * Freeze the contents of this class so that it can be written to
     * a file.
     */
    public void freeze() {
        assert !frozen;
        frozen = true;
    }

    /**
     * Writes the contents of the class to a file referenced by its name.
     * @param fileName The name of the file in which the class must be written.
     */
    public void writeTo(String fileName) throws IOException {
        writeTo(new File(fileName));
    }

    /**
     * Writes the contents of the class to a file.
     * @param file The file in which the class must be written.
     */
    public void writeTo(File file) throws IOException {
        File parent = file.getParentFile();
        if (parent != null && !parent.isDirectory())
            if (!parent.mkdirs())
                throw new IOException("cannot create directory " + parent);

        FileOutputStream fStream = new FileOutputStream(file);
        BufferedOutputStream bStream = new BufferedOutputStream(fStream);
        DataOutputStream dStream = new DataOutputStream(bStream);
        writeTo(dStream);
        dStream.close();
        bStream.close();
        fStream.close();
    }

    public void setBootstrapClass(String bootstrapClass) {
    	assert bootstrapClassAttr == null;
    	bootstrapClassAttr = new JBootstrapInvokeDynamic(context, this, bootstrapClass);
    	addAttribute(bootstrapClassAttr);
    }
    
    /**
     * Writes the contents of the class to a data stream.
     * @param stream The data stream in which the class must be written.
     */
    public void writeTo(DataOutputStream stream) throws IOException {
        if (!frozen) freeze();

        int thisClassIdx = pool.addClass(name);
        int superClassIdx = pool.addClass(superclassName);
        int[] interfacesIdx = new int[interfaceNames.length];

        for (int i = 0; i < interfaceNames.length; ++i)
            interfacesIdx[i] = pool.addClass(interfaceNames[i]);

        pool.freeze();

        // Magic number.
        stream.writeInt(MAGIC_NUMBER);
        // Version
        stream.writeShort(minor);
        stream.writeShort(major);
        // Constant pool
        pool.writeTo(stream);
        // Access flags
        stream.writeShort(accessFlags);

        // This class, super class and interfaces
        stream.writeShort(thisClassIdx);
        stream.writeShort(superClassIdx);
        stream.writeShort(interfacesIdx.length);
        for (int i = 0; i < interfacesIdx.length; ++i)
            stream.writeShort(interfacesIdx[i]);

        // Fields and methods
        stream.writeShort(fields.size());
        Iterator fieldsIt = fields.iterator();
        while (fieldsIt.hasNext())
            ((JField)fieldsIt.next()).writeTo(stream);

        stream.writeShort(methods.size());
        Iterator methodsIt = methods.iterator();
        while (methodsIt.hasNext())
            ((JMethod)methodsIt.next()).writeTo(stream);

        // Attributes
        JAttribute.writeTo(attributes, stream);
    }

    // Follows javap output format for ClassFile.
    /*@Override*/ public String toString() {
        StringBuffer buf = new StringBuffer();
        if (sourceFileName != null) {
            buf.append("Compiled from \"");
            buf.append(sourceFileName);
            buf.append("\"\n");
        }
        buf.append(getMemberName());
        buf.append(toExternalName(getName()));
        if (!isInterface()) {
            buf.append(" extends ");
            buf.append(toExternalName(getSuperclassName()));
        }
        if (interfaceNames.length > 0) {
            if (isInterface()) buf.append(" extends ");
            else buf.append(" implements ");
            for (int i = 0; i < interfaceNames.length; ++i) {
                if (i > 0) buf.append(",");
                buf.append(toExternalName(interfaceNames[i]));
            }
        }
        buf.append("\n");
        Iterator attrsIt = attributes.iterator();
        while (attrsIt.hasNext()) {
            JAttribute attr = (JAttribute)attrsIt.next();
            buf.append(attr);
        }
        buf.append("  minor version: ");
        buf.append(minor);
        buf.append("\n  major version: ");
        buf.append(major);
        buf.append("\n");
        buf.append(pool);
        buf.append("\n{\n");
        JField[] jfields = getFields();
        for (int i = 0; i < jfields.length; ++i) {
            if (i > 0) buf.append("\n");
            buf.append(jfields[i]);
        }
        buf.append("\n");
        JMethod[] jmethods = getMethods();
        for (int i = 0; i < jmethods.length; ++i) {
            if (i > 0) buf.append("\n");
            buf.append(jmethods[i]);
        }
        buf.append("\n}\n");
        return buf.toString();
    }

    private String getMemberName() {
        StringBuffer buf = new StringBuffer();
        if (isPublic()) buf.append("public ");
        else if (isProtected()) buf.append("protected ");
        else if (isPrivate()) buf.append("private ");
        if (isInterface())
            buf.append("interface ");
        else {
            if (isAbstract()) buf.append("abstract ");
            else if (isFinal()) buf.append("final ");
            buf.append("class ");
        }
        return buf.toString();
    }
}

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