A small makefile for building small Java projects and making runnable jars

Makefile

.PHONY: all clean run jar

JAR_NAME=Main.jar
MAIN_CLASS=Main
BIN_PATH=bin
LIB_PATH=lib

NOTHING=
SPACE=$(NOTHING) $(NOTHING)

LIBS=$(wildcard $(LIB_PATH)/*.jar)
CLASSPATH=$(BIN_PATH):$(subst $(SPACE),:,$(LIBS))
SOURCES=$(wildcard *.java)
CLASSES=$(addprefix $(BIN_PATH)/,$(SOURCES:.java=.class))

all: $(CLASSES)

$(BIN_PATH)/%.class: %.java
	javac -cp $(CLASSPATH) -d $(BIN_PATH) $<

run: all
	java -cp $(CLASSPATH) $(MAIN_CLASS)

clean:
	rm -rf $(BIN_PATH)
	rm -f $(JAR_NAME)

jar: all $(JAR_NAME)

$(JAR_NAME): $(LIBS)
	$(eval JAR_TEMP=$(shell mktemp -d))
	$(foreach lib,$(LIBS),unzip -o $(lib) -d $(JAR_TEMP);)
	rm -rf $(JAR_TEMP)/META-INF
	cp -R $(BIN_PATH)/* $(JAR_TEMP)/
	jar --create --file=$(JAR_NAME) --main-class=$(MAIN_CLASS) -C $(JAR_TEMP) .
	rm -rf $(JAR_TEMP)

I don't really recommend using this but I've needed it a few times 😅

Create a Main.java file with a public static void main(String... args) { in it in the same directory, create a lib directory and put any needed library jars in there.