### Question:
CommonHelper { public static void setSystemPropertyIfUnset(@NotNull String property, @NotNull String value) { if (System.getProperty(property) != null) { return; } if (System.getSecurityManager() != null) { AccessController.doPrivileged((PrivilegedAction<String>) () -> System.setProperty(property, value)); } else { System.setProperty(property, value); } } private  CommonHelper(); static MemoryMXBean memoryMXBean(); static ClassLoadingMXBean classLoadingMXBean(); static OperatingSystemMXBean operatingSystemMXBean(); static RuntimeMXBean runtimeMXBean(); static ThreadMXBean threadMXBean(); static long memoryPoolMXBeanCollectionUsage(); static Integer fromString(String s); static Boolean booleanFromString(String s); static Long longFromString(String s); static UUID tryParse(String s); static int longToInt(long in); static int calculateMaxMemory(); static int getTotalSystemMemory(); static String getIpAddress(@NotNull String input); static @Unmodifiable @NotNull Collection<String> getAllAvailableIpAddresses(); static void setSystemPropertyIfUnset(@NotNull String property, @NotNull String value); static @NotNull String formatThrowable(@NotNull Throwable throwable); static ReferencedOptional<T> findEnumField(Class<T> enumClass, String field); static final ExecutorService EXECUTOR; static final ScheduledExecutorService SCHEDULED_EXECUTOR_SERVICE; static final ArrayDeque<String> EMPTY_STRING_QUEUE; static final DateFormat DATE_FORMAT; static final DecimalFormat DECIMAL_FORMAT; }### Answer:
@Test void testSetSystemPropertyIfUnset() { System.setProperty("test", "test1"); CommonHelper.setSystemPropertyIfUnset("test", "test2"); Assertions.assertEquals("test1", System.getProperty("test")); CommonHelper.setSystemPropertyIfUnset("test1", "test1"); Assertions.assertEquals("test1", System.getProperty("test1")); }