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Targets and the entries in the dependency lists are the names of the files. Makefiles contain rules that describe how programs are built: Reference Bar and the timestamps on Bar.java and Bar.class are neverĬompared - Bar.java is NOT recompiled even though you have just modified the code!Ī makefile for this program is included below. However, when the program is recompiled (step 8),įoo.java is now up to date and is NOT compiled. Steps 6 and 7 also make Bar.java out of date.
#COMPILING JAVA FILE CODE#
The compiler finds a reference to class Foo, checks the timestamps on Foo.java andįoo.class, and finds that the source code file is out of date: it compiles Foo.java. After steps 2 and 3įoo.java is newer than Foo.class. Class FooBar (inįooBar.java) refers to class Foo (in Foo.java). class files do exist, then things are a bit more complex. class files do not exist, the corresponding. When a file is compiled, the Java compiler identifies the classes referenced within the file and looksįor corresponding. The change to Bar.java did not appear because the that file was NOT recompiled!.Recompile the program: javac FooBar.java.Remove the comments from the second println statement and save the file.Run the program and note the output: java FooBar.The following steps illustrate the problem: The kind that arise naturally while developing a large program) to show where it isn't true. It says, in part, that "you can think of the Java compiler as having the 'make' functionality alreadyīuilt in." This is almost true but it takes a carefully crafted sequence of edits and compiles (just class files (FooBar.class, Foo.class, and Bar.class). At the command line enter the following two commands: Local system where you may try the following experiments. So, how do we compile and run a programįollowing are four files: save them to a directory (i.e., folder) on your That implies that each class is typically placed in its own file. Generally, making a class public makes it easier to reuse at a later time. The idea is that the helper classes are only used with or by the public class It is often convenient to place a public class and any "helper" classes that it You may place more than one class in a single. Compiling and Running Mult-Class / Multi-File Programs