PrintableCharFinder { public static synchronized PrintableCharFinder getInstance() { if (instance == null) { instance = new PrintableCharFinder(); } return instance; } private  PrintableCharFinder(); static synchronized PrintableCharFinder getInstance(); boolean isPrintableChar(int codePoint); static void main(String... args);  }
@Test public void testGetInstance() throws Exception { PrintableCharFinder a = PrintableCharFinder.getInstance(); PrintableCharFinder b = PrintableCharFinder.getInstance(); assertEquals(a, b); }