Add removeAll to preferences (#987)

This removes all keys except for .type.

wpilibc/src/main/native/cpp/Preferences.cpp

@@ -222,3 +222,14 @@ bool Preferences::ContainsKey(wpi::StringRef key) {
  * @param key the key
  */
 void Preferences::Remove(wpi::StringRef key) { m_table->Delete(key); }
+
+/**
+ * Remove all preferences.
+ */
+void Preferences::RemoveAll() {
+  for (auto preference : GetKeys()) {
+    if (preference != ".type") {
+      Remove(preference);
+    }
+  }
+}

wpilibc/src/main/native/include/Preferences.h

@@ -52,6 +52,7 @@ class Preferences : public ErrorBase {
   void PutLong(wpi::StringRef key, int64_t value);
   bool ContainsKey(wpi::StringRef key);
   void Remove(wpi::StringRef key);
+  void RemoveAll();
 
  protected:
   Preferences();

wpilibj/src/main/java/edu/wpi/first/wpilibj/Preferences.java

@@ -173,6 +173,17 @@ public class Preferences {
     m_table.delete(key);
   }
 
+  /**
+   * Remove all preferences.
+   */
+  public void removeAll() {
+    for (String key : m_table.getKeys()) {
+      if (!".type".equals(key)) {
+        remove(key);
+      }
+    }
+  }
+
   /**
    * Returns the string at the given key. If this table does not have a value for that position,
    * then the given backup value will be returned.

wpilibjIntegrationTests/src/main/java/edu/wpi/first/wpilibj/PreferencesTest.java

@@ -7,6 +7,7 @@
 
 package edu.wpi.first.wpilibj;
 
+import java.util.Arrays;
 import org.junit.Before;
 import org.junit.Test;
 
@@ -88,6 +89,25 @@ public class PreferencesTest extends AbstractComsSetup {
     m_pref.putBoolean("checkedValueBoolean", true);
   }
 
+  /**
+   * Just checking to make sure our helper method works.
+   */
+  @Test
+  public void testRemove() {
+    remove();
+    assertEquals("Preferences was not empty!  Preferences in table: "
+        + Arrays.toString(m_pref.getKeys().toArray()),
+        1, m_pref.getKeys().size());
+  }
+
+  @Test
+  public void testRemoveAll() {
+    m_pref.removeAll();
+    assertEquals("Preferences was not empty!  Preferences in table: "
+        + Arrays.toString(m_pref.getKeys().toArray()),
+        1, m_pref.getKeys().size());
+  }
+
   @Test
   public void testAddRemoveSave() {
     assertEquals(m_pref.getLong("checkedValueLong", 0), 172L);