Move sleep skip to utils class

padlock-impl/src/main/java/com/cleverthis/interview/padlock/PadlockImpl.java

@@ -28,7 +28,6 @@ import static com.cleverthis.interview.padlock.Utils.ensureSleep;
  * After create, the input buffer is empty, you have to initialize.
  */
 public class PadlockImpl {
-    private final boolean fast = Boolean.parseBoolean(System.getProperty("fast"));
     private final int numpadSize;
     private final Integer[] inputBuffer;
     private final Integer[] correctPasscode;
@@ -66,7 +65,7 @@ public class PadlockImpl {
      * @return The old value, null if not initialized.
      */
     public synchronized Integer writeInputBuffer(int address, int keyIndex) {
-        if (!fast) ensureSleep(1000);
+        ensureSleep(1000);
         if (keyIndex < 0 || keyIndex >= numpadSize)
             throw new IllegalArgumentException(
                     "keyIndex out of range. Keypad size: " + numpadSize + ", keyIndex: " + keyIndex);

padlock-impl/src/main/java/com/cleverthis/interview/padlock/Utils.java

@@ -1,12 +1,24 @@
 package com.cleverthis.interview.padlock;
 
 class Utils {
+    /**
+     * Check if the sleep is disabled.
+     * User can use `-Dfast=true` in the jvm args,
+     * or change it on the fly.
+     * Might waste sometime on checking this flag, but the effect should be minor.
+     * */
+    private static boolean shouldSkipSleep() {
+        return Boolean.parseBoolean(System.getProperty("fast"));
+    }
+
     /**
      * Ensure we will wait a given amount of time even if there are interruptions.
+     * Property `-Dfast=true` can disable the sleep.
      *
      * @param millis The time you want to sleep, measure in millisecond.
      */
     public static void ensureSleep(long millis) {
+        if (shouldSkipSleep()) return;
         long endTime = System.currentTimeMillis() + millis;
         while (endTime > System.currentTimeMillis()) {
             try {