1. Common Errors
and Solutions
CST200 – Week 1: Common Errors when Starting
to write and compile Java Code
Instructor: Andreea Molnar

2. Outline
• Disclaimer
• Names
• Brackets
• Semicolons

3. Error Category

4. Names

5. Names (e.g. class names, variable names,
method names) are a single string!

6. public class Hello World {
}
Is the class
name Hello or
World?

7. public class Hello World {
}
After the first
string –Hello –
a bracket is
expected.

8. public class Hello World {
}

9. public class Hello World {
}

10. public class HelloWorld {
}
public class Hello {
}
public class World {
}

11. Keep in mind, it is not only class names,
variable names and method names have
to be composed of a single connected
string.

12. public class HelloWorld {
public static void main(String [] args) {
int Britteny Spears;
}
}

13. public class HelloWorld {
public static void main(String [] args) {
int Britteny Spears;
}
}
After the first
string –Brittney –
a ; is expected.

14. public class HelloWorld {
public static void main(String [] args) {
int Britteny Spears;
}
}

15. public class HelloWorld {
public static void main(String [] args) {
int BrittenySpears;
int Britteny;
int Spears;
}
}

16. public class HelloWorld {
public static void main(String [] args) {
//this is the best
int brittenySpears;
int britteny;
int spears;
}
}

17. Brackets

18. Every open bracket has to be closed in the
program!!!

19. As a rule of thumb check that every
bracket you open is closed somewhere in
the program: (), [], {}.

20. For the purpose of this class use curly
brackets –{}- at the beginning and the end
of a class and a method (more about
these in the next week).

21. Every open bracket has to be closed in the
program!!!

22. public class HelloWorld {
public static void main(String [] args) {
System.out.println(“Hello World”);
}
}

23. public class HelloWorld {
//beginning of the class body
public static void main(String [] args) {
System.out.println(“Hello World”);
}
} //end of the class body

24. public class HelloWorld {
public static void main(String [] args) {
//beginning of the method body
System.out.println(“Hello World”);
} //end of the method body
}

25. public class HelloWorld
public static void main(String [] args) {
System.out.println(“Hello World”);
}
}
Bracket
missing
Bracket expected

26. Enjoy finding the other errors.

27. Semicolons

28. You have to learn to love ; in Java. Every
statement in Java ends with a ;.

29. public class HelloWorld {
public static void main(String [] args) {
System.out.println(“Hello World”);
}
}

30. Summary
• Names are a single string.
• Brackets always come in pairs.
• Semicolons end a statement.

31. Thank you