请问大神一个相当基础的有关问题,为什么new线程执行报错,不new线程执行不报错

public static void main(String[] args) {
		new Thread(new OperateDB()).start();
}
class OperateDB implements Runnable{
	@Override
	public void run() {
		try {
			PoolManager.getInstance();
			String url="jdbc:microsoft:sqlserver://192.168.1.231:1434;DatabaseName=data_engine";
			Connection con = DriverManager.getConnection(url,"sa","scxn");
			Connection con2 = DriverManager.getConnection("jdbc:mysql://192.168.1.231:3308/world","root","scxn");
		} catch (SQLException e) {
			e.printStackTrace();
			PoolLogUtils.getInstance().writeLog("未知异常1:"+e.getMessage(),e.getCause().toString(),TestUtils.getDate());
		} catch (Exception e) {
			e.printStackTrace();
			PoolLogUtils.getInstance().writeLog("未知异常2:"+e.getMessage(),e.getCause().toString(),TestUtils.getDate());
		}
	}

public static void main(String[] args) {
		try {
			PoolManager.getInstance();
			String url="jdbc:microsoft:sqlserver://192.168.1.231:1434;DatabaseName=data_engine";
			Connection con = DriverManager.getConnection(url,"sa","scxn");
			Connection con2 = DriverManager.getConnection("jdbc:mysql://192.168.1.231:3308/world","root","scxn");
		} catch (SQLException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		} catch (Exception e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}
	}

com.mysql.jdbc.CommunicationsException: Communications link failure due to underlying exception: 

** BEGIN NESTED EXCEPTION ** 

com.mysql.jdbc.CommunicationsException
MESSAGE: Communications link failure due to underlying exception: 

** BEGIN NESTED EXCEPTION ** 

java.io.EOFException

STACKTRACE:

java.io.EOFException
	at com.mysql.jdbc.MysqlIO.readFully(MysqlIO.java:1913)
	at com.mysql.jdbc.MysqlIO.reuseAndReadPacket(MysqlIO.java:2304)
	at com.mysql.jdbc.MysqlIO.checkErrorPacket(MysqlIO.java:2803)
	at com.mysql.jdbc.MysqlIO.checkErrorPacket(MysqlIO.java:812)
	at com.mysql.jdbc.MysqlIO.doHandshake(MysqlIO.java:1235)
	at com.mysql.jdbc.Connection.createNewIO(Connection.java:2670)
	at com.mysql.jdbc.Connection.<init>(Connection.java:1531)
	at com.mysql.jdbc.NonRegisteringDriver.connect(NonRegisteringDriver.java:266)
	at java.sql.DriverManager.getConnection(Unknown Source)
	at java.sql.DriverManager.getConnection(Unknown Source)
	at OperateDB.run(TestMain.java:73)
	at java.lang.Thread.run(Unknown Source)


** END NESTED EXCEPTION **



Last packet sent to the server was 8 ms ago.

STACKTRACE:

com.mysql.jdbc.CommunicationsException: Communications link failure due to underlying exception: 

** BEGIN NESTED EXCEPTION ** 

java.io.EOFException

STACKTRACE:

java.io.EOFException
	at com.mysql.jdbc.MysqlIO.readFully(MysqlIO.java:1913)
	at com.mysql.jdbc.MysqlIO.reuseAndReadPacket(MysqlIO.java:2304)
	at com.mysql.jdbc.MysqlIO.checkErrorPacket(MysqlIO.java:2803)
	at com.mysql.jdbc.MysqlIO.checkErrorPacket(MysqlIO.java:812)
	at com.mysql.jdbc.MysqlIO.doHandshake(MysqlIO.java:1235)
	at com.mysql.jdbc.Connection.createNewIO(Connection.java:2670)
	at com.mysql.jdbc.Connection.<init>(Connection.java:1531)
	at com.mysql.jdbc.NonRegisteringDriver.connect(NonRegisteringDriver.java:266)
	at java.sql.DriverManager.getConnection(Unknown Source)
	at java.sql.DriverManager.getConnection(Unknown Source)
	at OperateDB.run(TestMain.java:73)
	at java.lang.Thread.run(Unknown Source)


** END NESTED EXCEPTION **



Last packet sent to the server was 8 ms ago.
	at com.mysql.jdbc.MysqlIO.reuseAndReadPacket(MysqlIO.java:2515)
	at com.mysql.jdbc.MysqlIO.checkErrorPacket(MysqlIO.java:2803)
	at com.mysql.jdbc.MysqlIO.checkErrorPacket(MysqlIO.java:812)
	at com.mysql.jdbc.MysqlIO.doHandshake(MysqlIO.java:1235)
	at com.mysql.jdbc.Connection.createNewIO(Connection.java:2670)
	at com.mysql.jdbc.Connection.<init>(Connection.java:1531)
	at com.mysql.jdbc.NonRegisteringDriver.connect(NonRegisteringDriver.java:266)
	at java.sql.DriverManager.getConnection(Unknown Source)
	at java.sql.DriverManager.getConnection(Unknown Source)
	at OperateDB.run(TestMain.java:73)
	at java.lang.Thread.run(Unknown Source)


** END NESTED EXCEPTION **



Last packet sent to the server was 9 ms ago.
	at com.mysql.jdbc.Connection.createNewIO(Connection.java:2741)
	at com.mysql.jdbc.Connection.<init>(Connection.java:1531)
	at com.mysql.jdbc.NonRegisteringDriver.connect(NonRegisteringDriver.java:266)