StringPreference.java

package org.hyperonline.hyperlib.pref;

import edu.wpi.first.wpilibj.Preferences;

import java.util.function.Supplier;

/**
 * A class which represents a string-valued preference
 *
 * @author James Hagborg
 */
public class StringPreference extends Preference implements Supplier<String> {
  private final String m_default;
  private String m_lastValue;

  /**
   * Create a {@link StringPreference} object tracking the preference with the given name and
   * default value. Calling this function does not yet modify the preferences file.
   *
   * @param name The string id of the preference
   * @param value The default value
   */
  public StringPreference(String name, String value) {
    super(name);

    if (value == null) {
      throw new NullPointerException("value == null");
    }

    m_lastValue = value;
    m_default = value;
  }

  /** {@inheritDoc} */
  @Override
  public synchronized boolean hasChanged() {
    String newValue = get();
    boolean changed = !newValue.equals(m_lastValue);
    m_lastValue = newValue;
    return changed;
  }

  /** {@inheritDoc} */
  @Override
  public void putDefaultValue() {
    Preferences.setString(getName(), m_default);
  }

  /**
   * Get the current value of the preferences file entry, or the default if no entry exists.
   *
   * @return The value of the preference
   * @see Preferences#getString(String, String)
   */
  @Override
  public String get() {
    return Preferences.getString(getName(), m_default);
  }
}