聊聊druid的源码的几个疑问

    public void close() throws SQLException {
        if (this.disable) {
            return;
        }

        DruidConnectionHolder holder = this.holder;
        if (holder == null) {
            if (dupCloseLogEnable) {
                LOG.error("dup close");
            }
            return;
        }

        DruidAbstractDataSource dataSource = holder.getDataSource();
        boolean isSameThread = this.getOwnerThread() == Thread.currentThread();

        if (!isSameThread) {
            dataSource.setAsyncCloseConnectionEnable(true);
        }

        if (dataSource.isAsyncCloseConnectionEnable()) {
            syncClose();
            return;
        }

        //......
    }    

	protected volatile int numTestsPerEvictionRun = DEFAULT_NUM_TESTS_PER_EVICTION_RUN;

	public static final int DEFAULT_NUM_TESTS_PER_EVICTION_RUN = 3;

    public int getNumTestsPerEvictionRun() {
        return numTestsPerEvictionRun;
    }

    /**
     * @param numTestsPerEvictionRun
     */
    @Deprecated
    public void setNumTestsPerEvictionRun(int numTestsPerEvictionRun) {
        this.numTestsPerEvictionRun = numTestsPerEvictionRun;
    }

protected volatile long timeBetweenEvictionRunsMillis = DEFAULT_TIME_BETWEEN_EVICTION_RUNS_MILLIS;

public static final long DEFAULT_TIME_BETWEEN_EVICTION_RUNS_MILLIS = 60 * 1000L;

    public DruidPooledConnection getConnectionDirect(long maxWaitMillis) throws SQLException {
    	for (; ; ) {
    		// get connection
    		if (testOnBorrow) {
    			// testConnectionInternal
    		} else {
    			if (testWhileIdle) {
                    long idleMillis = currentTimeMillis - lastActiveTimeMillis;

                    long timeBetweenEvictionRunsMillis = this.timeBetweenEvictionRunsMillis;

                    if (timeBetweenEvictionRunsMillis <= 0) {
                        timeBetweenEvictionRunsMillis = DEFAULT_TIME_BETWEEN_EVICTION_RUNS_MILLIS;
                    }
                    if (idleMillis >= timeBetweenEvictionRunsMillis
                            || idleMillis < 0 // unexcepted branch
                    ) {
                        boolean validate = testConnectionInternal(poolableConnection.holder, poolableConnection.conn);
                        if (!validate) {
                            if (LOG.isDebugEnabled()) {
                                LOG.debug("skip not validate connection.");
                            }

                            discardConnection(poolableConnection.holder);
                            continue;
                        }
                    }
    			}
    		}

    		//......
    	}

    }