deep.java

是有关解释器的.用JAVA编写.可以解释一般的JAVA程序.

import java.lang.reflect.*;
import java.util.*;

/**
 * This class uses java reflection to create "deep" copies of objects. "deep"
 * means, that not the references are copied but the references objects are
 * cloned as well.
 * 
 * @see #copy( Object )
 */
public class Deep {
    private static java.lang.reflect.Method nativeNewInstance() {
        Class clazz = java.io.ObjectInputStream.class;
        java.lang.reflect.Method method = null;

        try {
            method = clazz.getDeclaredMethod("allocateNewObject", new Class[] {
                    Class.class, Class.class });
            method.setAccessible(true);
        } catch (Exception exception) {
        }

        return method;
    }

    private static java.lang.reflect.Method allocateNewObject = nativeNewInstance();

    private Object getInstance(Class clazz) {
        if (allocateNewObject == null) {
            try {
                return clazz.newInstance();
            } catch (Exception exception) {
            }
        }
        try {
            return allocateNewObject.invoke(null, new Object[] { clazz,
                    Object.class });
        } catch (Exception exception) {
        }
        return null;
    }

    /**
     * Creates a deep copy of the given element. "primitive" attributes are
     * copied, references are recursivly deep-cloned. The returned object can be
     * casted to the type of the given object.
     * 
     * @param toCopy
     *            object to be deeply cloned
     * @return the cloned object or null if cloning failed.
     */
    static public Object copy(Object toCopy) {
        return (new Deep()).internalCopy(toCopy, new LinkedList());
    }

    private Object internalCopy(Object toCopy, LinkedList oAlreadyCopied) {
        Class oClass, oCurrentClass;
        Field[] oFields;
        Object result = new Object();

        if (toCopy == null) {
            // 1. The object to be copied might be null. Don't need to copy
            // something then: return null
            return null;
        } else if (inList(toCopy, oAlreadyCopied) != null) {
            // 2. If the object is in the list of all abjects already copied,
            // return its copy
            return inList(toCopy, oAlreadyCopied);
        } else {
            // 3. If the object is not null and not already copied, copy it and
            // put it into the list
            oClass = toCopy.getClass();

            if (oClass.isArray()) {
                // toCopy is an Array, so build new Array and copy all elements

                result = Array.newInstance(oClass.getComponentType(), Array
                        .getLength(toCopy));

                for (int i = 0; i < Array.getLength(toCopy); i++) {
                    Array.set(result, i, internalCopy(Array.get(toCopy, i),
                            oAlreadyCopied));
                }

            } else {
                // toCopy is no Array

                if (oClass.getName().equals("java.lang.Boolean")) {
                    // toCopy is wrapper of a boolean
                    result = new Boolean(((Boolean) toCopy).booleanValue());
                } else if (oClass.getName().equals("java.lang.Integer")) {
                    // toCopy is wrapper of an int
                    result = new Integer(((Integer) toCopy).intValue());
                } else if (oClass.getName().equals("java.lang.Double")) {
                    // toCopy is wrapper of a double
                    result = new Double(((Double) toCopy).doubleValue());
                } else if (oClass.getName().equals("java.lang.Float")) {
                    // toCopy is wrapper of a float
                    result = new Float(((Float) toCopy).floatValue());
                } else if (oClass.getName().equals("java.lang.Byte")) {
                    // toCopy is wrapper of a byte
                    result = new Byte(((Byte) toCopy).byteValue());
                } else if (oClass.getName().equals("java.lang.Character")) {
                    // toCopy is wrapper of a char
                    result = new Character(((Character) toCopy).charValue());
                } else if (oClass.getName().equals("java.lang.Long")) {
                    // toCopy is wrapper of a long
                    result = new Long(((Long) toCopy).longValue());
                } else if (oClass.getName().equals("java.lang.Short")) {
                    // toCopy is wrapper of a short
                    result = new Short(((Short) toCopy).shortValue());
                } else {
                    // toCopy is no wrapper, so get all declared Fields of this
                    // class and all superclasses and copy them
                    result = getInstance(oClass);
                    oCurrentClass = toCopy.getClass();
                    while (oCurrentClass != null) {
                        oFields = oCurrentClass.getDeclaredFields();
                        for (int i = 0; i < oFields.length; i++) {
                            oFields[i].setAccessible(true);
                            // toDo: Filter static fields? Perhaps other
                            // modiefiers should be filtered too
                            try {
                                if ((oFields[i].get(toCopy) != null)
                                        && !(Modifier.isFinal(oFields[i]
                                                .getModifiers()))) {
                                    oFields[i].set(result, internalCopy(
                                            oFields[i].get(toCopy),
                                            oAlreadyCopied));
                                }
                            } catch (Exception exception) {
                            }
                        }
                        oCurrentClass = oCurrentClass.getSuperclass();
                    } // end while ( oCurrentClass != null )
                } // end if ( oClass.getName().equals( "java.lang.Boolean" ) )

            } // end if ( toCopy.isArray)

            addToList(toCopy, result, oAlreadyCopied);

            return result;
        }

    }

    private Object inList(Object toLookUp, LinkedList oAlreadyCopied) {

        ListIterator oIterator = oAlreadyCopied.listIterator(0);
        Object oCurrent;
        boolean result = false;

        while (oIterator.hasNext()) {
            oCurrent = oIterator.next();
            if (((CopiedObject) oCurrent).isSame(toLookUp))
                return ((CopiedObject) oCurrent).getCopy();
        }

        return null;
    }

    private void addToList(Object original, Object copy,
            LinkedList oAlreadyCopied) {

        oAlreadyCopied.add(new CopiedObject(original, copy));

    }

    private class CopiedObject {

        private Object original;
        private Object copied;

        private CopiedObject(Object original, Object copied) {
            this.original = original;
            this.copied = copied;
        }

        private boolean isSame(Object other) {
            return (this.original == other);
        }

        private Object getCopy() {
            return copied;
        }

    }

}