private MemoryUtil() {
    }

    /**
     * Gets a formatted memory usage log string.
     *
     * @return formatted memory usage information
     */
    public static String getMemoryUsageLog() {
        final Runtime runtime = Runtime.getRuntime();
        final long freeBytes = runtime.freeMemory();
        final long maxBytes = runtime.maxMemory();
        final long totalBytes = runtime.totalMemory();

        assertEquals(132L, MemoryUtil.sizeOf(Maps.map("1234567890", "1234567890").$()));
    }

    @Test
    public void test_getMemoryUsageLog() {
        String log = MemoryUtil.getMemoryUsageLog();

        assertNotNull(log);
        assertTrue(log.startsWith("Mem:{used "));
        assertTrue(log.contains(", heap "));
        assertTrue(log.contains(", max "));
        assertTrue(log.endsWith("}"));

                            MemoryUtil.getMemoryUsageLog());
                } else {
                    logger.info("Sent {} documents (send={}ms, {})", docList.size(), systemHelper.getCurrentTimeAsLong() - execTime,
                            MemoryUtil.getMemoryUsageLog());
                }
            }
        } finally {
            docList.clear();
        }

            if (cleanupTime >= 0) {
                buf.append(", cleanup ").append(cleanupTime).append("ms");
            }
            buf.append("}, ");
            buf.append(MemoryUtil.getMemoryUsageLog());
            buf.append(')');
            logger.info(buf.toString());
        }
        final long unprocessedDocumentSize = fessConfig.getIndexerUnprocessedDocumentSizeAsInteger().longValue();

        System.gc();
        long current = MemoryUtil.getUsedMemory();
        for (int i = 0; i < 10000; i++) {
            if (i % 1000 == 0) {
                logger.info("count:" + i + ", " + MemoryUtil.getMemoryUsageLog());
            }
            ResponseData responseData = new ResponseData();
            responseData.setCharSet("UTF-8");
            responseData.setContentLength(data.length());