How to Create a Java program课件.pptVIP

COMPILING AND RUNNING A JAVA PROGRAM Now we are ready to interpret (or “execute” as the term used in other programming languages). On a DOS pane call the interpreter (called java) i.e. C:\CS115\MyPrograms\ java MyFirstProgram Notes: java is the command for the interpreter. Your bytecodes file name is used without any extension. The output of the program will appear on the DOS window(pane). We could, however, get errors during execution, called: “RUNTIME ERRORS”. 精品文档 COMPILING AND RUNNING A JAVA PROGRAM Runtime Errors These are errors that take place during the time the program runs (these errors can not be caught by the compiler). Quite often they are referred to as “exceptions” Usually the result of programmer’s mistakes. They are reported by Java’ s runtime environment called JVM (Java Virtual Machine). Need to go back to the source code file and correct them, then re compile and try to interpret again. The interpreter will give you messages (usually cryptic) regarding the runtime errors. Sometimes we can make sense out of the message, but other times we have to kind of guess. 精品文档 COMPILING AND RUNNING A JAVA PROGRAM If there are no compiler or runtime errors, it is possible to get another category or errors called “LOGICAL ERRORS” (in spite of the fact that your program was inetrpreted) It is possible that you are not getting any errors but your program does not give you the correct result. This is due to your logical errors when you wrote the code: i.e. Suppose that you meant to add but instead you multiplied two numbers. 精品文档 STRUCTURE OF A JAVA PROGRAM Your java source code should have the following sections: Import statements (not always needed) The class name “Global” variables declared (not always needed). Also called instance variables. Methods inside the class One of those methods must be the main method Inside the method we have “local” variables declared and the source code for the method. Note: Don’t worry about the terms: import statements,