Checkstyle 可寻找：·不能使用的或者多余的输入 ·空格更好的地方不使用跳格符

				//Tested with BCEL-5.1
				//http://jakarta.apache.org/builds/jakarta-bcel/release/v5.1/
				
				package com.puppycrawl.tools.checkstyle.bcel.classfile;
				
				import java.util.HashSet;
				import java.util.Set;
				
				import org.apache.bcel.classfile.Field;
				
				import com.puppycrawl.tools.checkstyle.bcel.generic.FieldReference;
				import com.puppycrawl.tools.checkstyle.bcel.generic.PUTFIELDReference;
				import com.puppycrawl.tools.checkstyle.bcel.generic.PUTSTATICReference;
				
				/**
				 * Contains the definition of a Field and its references.
				 * @author Rick Giles
				 */
				public class FieldDefinition
				    extends FieldOrMethodDefinition
				{
				    /** the GET references for the Field */
				    private final Set mGetReferences = new HashSet();
				
				    /** the PUT references for the FSield */
				    private final Set mPutReferences = new HashSet();
				
				    /**
				     * Creates a FieldDefinition for a Field.
				     * @param aField the Field.
				     */
				    public FieldDefinition(Field aField)
				    {
				        super(aField);
				    }
				
				    /**
				     * Returns the Field for this definition.
				     * @return the Field for this definition.
				     */
				    public Field getField()
				    {
				        return (Field) getFieldOrMethod();
				    }
				
				    /**
				     * Determines the number of read, or GET, references to the Field.
				     * @return the number of read references to the Field.
				     */
				    public int getReadReferenceCount()
				    {
				        return mGetReferences.size();
				    }
				
				    /**
				     * Determines the number of write, or PUT, references to the Field.
				     * @return the number of write references to the Field.
				     */
				    public int getWriteReferenceCount()
				    {
				        return mPutReferences.size();
				    }
				
				    /**
				     * Determines the total number of references to the Field.
				     * @return the number of references to the Field.
				     */
				    public int getReferenceCount()
				    {
				        return getReadReferenceCount() + getWriteReferenceCount();
				    }
				
				    /**
				     * Adds a reference to the Field.
				     * @param aFieldRef the reference.
				     */
				    public void addReference(FieldReference aFieldRef)
				    {
				        // TODO Polymorphize
				        if ((aFieldRef instanceof PUTFIELDReference)
				            || (aFieldRef instanceof PUTSTATICReference))
				        {
				            mPutReferences.add(aFieldRef);
				        }
				        else {
				            mGetReferences.add(aFieldRef);
				        }
				    }
				}