java报错awt-eventqueue-0

Question

String abc=null;
			String abc1=null;
			Connection connect = DriverManager.getConnection("jdbc:mysql://localhost:3306/tcs?severTimezone=GMT","root","root");
			Statement stmt = connect.createStatement();
			Statement stmt1 = connect.createStatement();
			String id13=id10.getText().toString();
			String user13=user10.getText().toString();
			if(!id13.equals("")&&!user13.equals("")){
			
			String password13=password10.getText().toString();
			
			ResultSet rs=stmt.executeQuery("select id from user where id='"+id13+"'");
			while(rs.first()){ abc=rs.getString(1);}
			
			ResultSet rs1=stmt1.executeQuery("select name from user where name='"+user13+"'");
			while(rs1.first()){ abc1=rs1.getString(1);}
			if(abc.equals(""))System.out.println("123");
			if(true){
			stmt.executeUpdate("insert into user values('"+id13+"','"+user13+"','"+password13+"')");
			JOptionPane.showMessageDialog(null, "注册成功");
			}else JOptionPane.showMessageDialog(null, "号码或用户名已有人使用");
			}else JOptionPane.showMessageDialog(null, "号码和用户名不可为空");

Answer 1

abc变量是哪里来的，没有初始值，abc应该是一个String类型变量吧。