deccode data from a magnetic striped card data

UsbDecoder.java

package org.andreis.daniele.myApp;

import android.util.Log;

/**
 * Created by daniele
 */

public class UsbDecoder {
    private String rawData = null;
    private String field3 = null;
    private String field2 = null;
    private String field1 = null;
    private boolean isComplete = false;
    private boolean isStart = false;
    private int position = 0;
    private char marker = '!';

    public void UsbDecoder(String rawData) {
        this.rawData = rawData;

    }

    public String getField1() {
        return field1;
    }

    public String getField2() {
        return field2;
    }

    public String getField3() {
        return field3;
    }

    public boolean addChar(Character c) {
        if (isComplete) {
            reset();
        }

        int cUnicode = (int) c;
        if (!Character.isWhitespace(cUnicode)) {
            if (c.equals(marker) && (rawData == null || rawData.isEmpty())) {
                rawData = String.valueOf(c);
                isStart = true;
            } else if (c.equals(marker) && isStart) {
                rawData = rawData + c;
                isComplete = true;
                decode();
            } else if (isStart && Character.isLetterOrDigit(cUnicode)) {
                rawData = rawData + c;
            }
        }
        if(Character.isWhitespace(c) && rawData!=null){
            position = rawData.length();
        }

        return isComplete;
    }


    private void reset() {
        rawData = null;
        field1 = null;
        field2 = null;
        field3 = null;
        isComplete = false;
        isStart = false;
    }


    private void decode() {
        if (rawData.length() > 19) {
            this.field1 = rawData.substring(1, 17);
            if (position > 17) {
                this.field2 = rawData.substring(17, position);
                this.field3 = rawData.substring(position, rawData.length() - 1);
            }
        }
    }

}