Running Java in Xcode.. don't ask me why 🤷‍♂️. Taken from: https://discussions.apple.com/docs/DOC-5161.

JavaInXcode.java

import UIKit

// 🤔
class ChangeConstants {
  private final int[] orderedCoinLabels = { FIFTY_POUNDS_VALUE,
  TWENTY_POUNDS_VALUE,
  TEN_POUNDS_VALUE,
  FIVE_POUNDS_VALUE,
  TWO_POUNDS_VALUE,
  ONE_POUND_VALUE,
  FIFTY_PENCE_VALUE,
  TWENTY_PENCE_VALUE,
  TEN_PENCE_VALUE,
  FIVE_PENCE_VALUE,
  TWO_PENCE_VALUE,
  PENCE_VALUE
  };
}

public class HelloWorld
  {
  public static void main(String[] args)
    {
    int label = orderedCoinLabels[0];
    System.out.println("Hello, this is my label number: " + label);
    }
  }

Makefile

# A simple makefile for a Hello World Java program

# Define a makefile variable for the java compiler
JCC = javac

# Define a makefile variable for compilation flags
# The -g flag compiles with debugging information
JFLAGS = -g

# typing 'make' will invoke the first target entry in the makefile
# (the default one in this case)
default: $(subst .java,.class,$(wildcard *.java))

# this target entry builds the Average class
# the Average.class file is dependent on the Average.java file
# and the rule associated with this entry gives the command to create it
#
%.class : %.java
          $(JCC) $(JFLAGS) $<

# To start over from scratch, type 'make clean'. 
# Removes all .class files, so that the next make rebuilds them
#
clean:
          $(RM) *.class