Java Object Collection To String With Delimiter and Optional Field Usage For Object Values

gistfile1.txt

/**
 * Convert list to string with delimiter
 * @param <T> class of the collection
 * @param values Given long values
 * @param classTypeParam Pass class type to get fields, do not set null
 * @param fieldName Name of the field of the object to get value of
 * @param delimiter Given delimiter
 * @return ({1L,3L,5L} + Long.class + null + ",") --> ("1,3,5")
 *         ({{id:1},{id:2},{id:3}} + ObjectClass.class + "id" + ",") --> ("1,2,3")
 */
public static <T> String collectionToString(Collection<T> values, Class<T> classTypeParam, String fieldName, String delimiter) {
    if (values == null || values.size() == 0) {
        return "";
    } else {
        int fieldIndex = 0;
        boolean useField = !StringUtils.isNullOrEmpty(fieldName);
        Field[] fields = classTypeParam.getDeclaredFields();
        if (useField) {
            while (!fields[fieldIndex].getName().equals(fieldName))
                fieldIndex++;
        }
        StringBuilder sb = new StringBuilder();
        int index = 0;
        for (T value: values) {
            if (useField) {
                try {
                    sb.append(fields[fieldIndex].get(fieldName));
                } catch (IllegalArgumentException | IllegalAccessException e) {
                    sb.append(value);
                }
            } else {
                sb.append(value);
            }
            if (index < values.size() - 1) {
                sb.append(delimiter);
            }
            index++;
        }
        return sb.toString();
    }
}