Java makefile example

Creating a Makefile for a set of Java files

Here is an example makefile for a Java program that uses a few class files:

JFLAGS = -g
JC = javac
.SUFFIXES: .java .class
.java.class:
        $(JC) $(JFLAGS) $*.java

CLASSES = \
        Purchaser.java \
        PurchaserList.java \
        PurchaserListTest.java \
        SortedList.java \
        Supplier.java \
        SupplierList.java \
        LinearList.java 

default: classes

classes: $(CLASSES:.java=.class)

clean:
        $(RM) *.class

To use the above makefile to compile your java programs:

create a file named 'makefile' in your lab directory with the same content as this example
modify the CLASSES macro so that it has the names of your .java files;
run 'make', and if all goes well, it should compile all of your java source files that need to be re-built.

Here is the same makefile, with comments explaining each line:


# define a variable for compiler flags (JFLAGS)
# define a variable for the compiler (JC)  
#

JFLAGS = -g
JC = javac

#
# Clear any default targets for building .class files from .java files; we 
# will provide our own target entry to do this in this makefile.
# make has a set of default targets for different suffixes (like .c.o) 
# Currently, clearing the default for .java.class is not necessary since 
# make does not have a definition for this target, but later versions of 
# make may, so it doesn't hurt to make sure that we clear any default 
# definitions for these
#

.SUFFIXES: .java .class

#
# Here is our target entry for creating .class files from .java files 
# This is a target entry that uses the suffix rule syntax:
#	DSTS:
#		rule
# DSTS (Dependency Suffix Target Suffix)
# 'TS' is the suffix of the target file, 'DS' is the suffix of the dependency 
#  file, and 'rule'  is the rule for building a target	
# '$*' is a built-in macro that gets the basename of the current target 
# Remember that there must be a < tab > before the command line ('rule') 
#

.java.class:
        $(JC) $(JFLAGS) $*.java

#
# CLASSES is a macro consisting of several words (one for each java source file)
#   the backslash "\" at the end of the line is a line continuation character
*    so that the same line can continue over several lines

CLASSES = \
        Purchaser.java \
        PurchaserList.java \
        PurchaserListTest.java \
        SortedList.java \
        Supplier.java \
        SupplierList.java \
        LinearList.java

#
# the default make target entry
# for this example it is the target classes

default: classes

# Next line is a target dependency line
# This target entry uses Suffix Replacement within a macro: 
# $(macroname:string1=string2)
# In the words in the macro named 'macroname' replace 'string1' with 'string2'
# Below we are replacing the suffix .java of all words in the macro CLASSES 
# with the .class suffix
#

classes: $(CLASSES:.java=.class)

# this line is to remove all unneeded files from
# the directory when we are finished executing(saves space)
# and "cleans up" the directory of unneeded .class files
# RM is a predefined macro in make (RM = rm -f)
#

clean:
        $(RM) *.class