Turn Java objects into Strings.

StringifyObject.java

import java.lang.reflect.Field;
import java.util.Arrays;
import java.util.HashSet;
import java.util.LinkedList;
import java.util.List;
import java.util.Map;

public class StringifyObject {

    private HashSet<Integer> objects = new HashSet<>();

    private StringifyObject() {

    }

    public static String stringify( Object o ) throws IllegalAccessException {
        StringifyObject stringifyObject = new StringifyObject();
        return stringifyObject.stringifyObject( o );
    }

    private static List<Field> getAllFields( Class<?> type ) {
        return getAllFields( new LinkedList<Field>(), type );
    }

    private static List<Field> getAllFields( List<Field> fields, Class<?> type ) {
        fields.addAll( Arrays.asList( type.getDeclaredFields() ) );

        if( type.getSuperclass() != null ) {
            fields = getAllFields( fields, type.getSuperclass() );
        }

        return fields;
    }

    private String stringifyObject( Object o ) throws IllegalAccessException {
        if( o == null ) {
            return "null";
        }

        int objectHash = System.identityHashCode( o );

        if( objects.contains( objectHash ) ) {
            return "obj@" + String.valueOf( objectHash );
        }

        objects.add( objectHash );

        StringBuilder sb                  = new StringBuilder();
        boolean       toStringImplemented = false;
        try {
            //toString not declared by this class, so it hasn't been implemented
            if( o.getClass() == o.getClass().getMethod( "toString" ).getDeclaringClass() ) {
                toStringImplemented = true;
            }
        } catch( NoSuchMethodException e ) {

        }
        sb.append( "[" );
        sb.append( o.getClass().getName().replace( "[", "Array" ) );
        sb.append( "@" );
        sb.append( System.identityHashCode( o ) );
        sb.append( ":{" );

        if( toStringImplemented ) {
            sb.append( o.toString() );
        } else if( o instanceof Enum ) {
            sb.append( ( (Enum) o ).name() );
        } else if( o instanceof Iterable ) {
            for( Object e : (Iterable) o ) {
                sb.append( stringifyObject( e ) );
            }
        } else if( o.getClass().isArray() ) {
            switch( o.getClass().getName() ) {
                case "[Z":
                    for( boolean e : (boolean[]) o ) {
                        sb.append( "[" );
                        sb.append( e );
                        sb.append( "]" );
                    }
                    break;
                case "[B":
                    for( byte e : (byte[]) o ) {
                        sb.append( "[" );
                        sb.append( e );
                        sb.append( "]" );
                    }
                    break;
                case "[S":
                    for( short e : (short[]) o ) {
                        sb.append( "[" );
                        sb.append( e );
                        sb.append( "]" );
                    }
                    break;
                case "[I":
                    for( int e : (int[]) o ) {
                        sb.append( "[" );
                        sb.append( e );
                        sb.append( "]" );
                    }
                    break;
                case "[J":
                    for( long e : (long[]) o ) {
                        sb.append( "[" );
                        sb.append( e );
                        sb.append( "]" );
                    }
                    break;
                case "[F":
                    for( float e : (float[]) o ) {
                        sb.append( "[" );
                        sb.append( e );
                        sb.append( "]" );
                    }
                    break;
                case "[D":
                    for( double e : (double[]) o ) {
                        sb.append( "[" );
                        sb.append( e );
                        sb.append( "]" );
                    }
                    break;
                case "[C":
                    for( char e : (char[]) o ) {
                        sb.append( "[" );
                        sb.append( e );
                        sb.append( "]" );
                    }
                    break;
                case "[L":
                default:
                    if( o.getClass().getName().startsWith( "[L" ) ) {
                        for( Object e : (Object[]) o ) {
                            sb.append( stringifyObject( e ) );
                        }
                    } else {
                        throw new RuntimeException( o.getClass().getName() + " is unimplemented :(" );
                    }
            }
        } else if( o instanceof Map ) {
            for( Object e : ( (Map) o ).keySet() ) {
                sb.append( "[" );
                sb.append( stringifyObject( e ) );
                sb.append( "," );
                sb.append( stringifyObject( ( (Map) o ).get( e ) ) );
                sb.append( "]" );
            }
        } else {
            for( Field f : getAllFields( o.getClass() ) ) {
                if( !f.isAccessible() ) {
                    f.setAccessible( true );
                }
                sb.append( "[" );
                sb.append( f.getName().replace( "[", "Array" ) );
                sb.append( ":" );
                sb.append( stringifyObject( f.get( o ) ) );
                sb.append( "]" );
            }
        }
        sb.append( "}]" );
        return sb.toString();
    }
}