Java by default means

• mutable objects: person.setName

  • references to mutable objects
    • overriding equals and hashCode

• statements > expressions:

  doX();
  doY();

• RuntimeExceptions en masse

• bad error messages

• mutable variables: setName(final String name)

• package public members:

  • private String name;
  • (implicit) constructors

• extensible classes: final class Person;

• no exhaustive type matching (only as a java 17 preview feature)

• eager evaluation

• unreadable formatting

  • actually useful info near the end of the line:

    public final class <Example> {
        public static void <main(String[] args)> {
            System.out.<println("Hello world")>;
        }
    }

  • all-caps:

    enum Fruit { BANANA }
    static final Fruit YELLOW_FRUIT= BANANA;

  • 1-letter type variable names:

    <T, U, V> V
    map2(...<T> ..., ...<U> ...)

• verbosity

• gotchas:

  'h' + 'e' + 'l' + 'l' + 'o' // == 532

... it's easy to write bad code in java.

After a year with elm, I disagree with nearly every basic design decision.

If you are required to use java – just like me, here are some tips to make the best of java:

• union-type
• final-everywhere*
• static functions
• formatting

Note: This list covers only a few tips.