Question

i wanted to practice developing database programs in java so i set the classpath to E:\software\installed\java\jre\lib by declaring a new environmental variable classpath and gave value as E:\software\installed\java\jre\lib but now i am unable to run any program(not even non-database) i get an error

Error: Could not find or load main class MysqlConnect

but when i delete the classpath variable i am able to run non-database programs. what is the possible problem and please let me know the solution. i have set path to E:\software\installed\java\bin

nothing is helping i tried using class path switch in java which is not helping (java -cp C:\Program Files\MySQL\MySQL Server 5.5 MysqlConnect) nor do setting path is helping (set CLASSPATH=%CLASSPATH%:C:\Program Files\MySQL\MySQL Server 5.5:C:\Program Files\MySQL\MySQL Server 5.5\mysql-connector-java-5.1.20-bin.jar) all are giving the error

Error: Could not find or load main class MysqlConnect

Answer 1

You shouldn’t be defining a classpath for your programs using system variables. Standard way is to use the command line -cp or -classpath option. Take a look at what java prints out if you run it with no arguments.

You will find this mentioned in this tutorial. It says:

The preferred way to specify the class path is by using the -cp command line switch. This allows the CLASSPATH to be set individually for each application without affecting other applications. Setting the CLASSPATH can be tricky and should be performed with care

Also, see how the default CLASSPATH environmetn variable has a . in it. If you still decide to add your classes in there, keep the . for other citizens and add your classes after a ;, don’t just overwrite the whole value.