switch statements

[glelouet]

the new switch (with -> ) allows for many changes besides the symbol

• return a value (can be void as the usual one) double d = switch(o) {…}
• allows variable declaration with pattern matching case int i -> i+1
• guarding case float f when f>0 ->…
• provides yield for block case char c-> {countChar++;yield count;}
• null case allowed case null -> …
• deconstruction of records case Segment(Point2D(int x1, int y1), Point2D(int x2, int y2))-> …

https://docs.oracle.com/en/java/javase/25/language/pattern-matching-switch.html

[glelouet]

My idea of implementation :

	public void basicSwitch(JPackage root, JCodeModel jcm) throws JCodeModelException {
		JDefinedClass cl = root._class("BasicSwitch");
		JMethod m = cl.method(JMod.PUBLIC, Number.class, "plus1");
		JVar o = m.varParam(jcm.ref(Object.class), "o");
		sw = JExpr._switch(o);

		// java 26 ?
		// case 0, -0-> -1 ;
		sw._case(JExpr.lit(0))
				._case(JExpr.lit(-0))
				.yield(JExpr.lit(-1));

		// java 21
		// case Integer i ->i+1
		// we name variable but could be i. This is the "case" variable
		sw._case(Integer.class, "i").yield(variable -> JOp.plus(variable, JExpr.lit(1)));

		// java 21
		// case Character c when c >= '0' && c <= '9' -> c - '0' + 1;
		sw._case(Character.class, "c")
				.when(c -> JOp.gte(c, Jexpr.lit('0')))
				.when(c -> JOp.lte(c, Jexpr.lit('9')))
				.yield(c -> JOp.plus(JOp.min(varible, JExpr.lit('0')), JExpr.lit(1)));

		// java 26 ?
		// case char c -> 1 + c;
		sw._case(char.class, "c")
				.yield(c -> JOp.plus(c, JExpr.lit(1)));

		// java 21
		// case null -> {nullCount++;yield nullCount;}
		JFieldVar nullCountVar = cl.field(JMod.PRIVATE, int.class, "nullCount");
		/// null case is special because it can be merged with default, `case default,
		/// null ->`
		sw._null()
				.add(JExpr.incr(nullCountVar))
				.yield(nullCountVar);

		// java 17
		// default- > throw new UnsupportedOperationException();
		sw._default()._throws(UnsupportedOperationException.class, JOp.plus("case not handled : ", o));

		// java 17
		// return switch(o){ … };
		m.body()._return(sw);
	}


	// the code we want
	private int nullCount;
	public Number plus1(Object o) {
		return switch (o) {
		case 0, -0 -> -1;
		case Integer i -> i + 1;
		case Character c when c >= '0' && c <= '9' -> c - '0' + 1;
		case char c -> 1 + c;
		case null -> {
			nullCount++;
			yield nullCount;
		}
		default -> throw new UnsupportedOperationException("case not handled : " + o);
		};
	}

[glelouet]

started
master...glelouet:jcodemodel:switchexpression

[glelouet]

ok so I can't test switch pattern because it's java 21.
I set java.version to 21
Now I have issues because deprecated URL constructor is called.
So I switch to an url.of(uri, handler) . But it does not allow to create realtive URI anymore, in my dynamicclassloader I save the resources by RELATIVE path so the returned URL refers to an absolute path which can''t be resolves to the resources's data - so tests fail.

-.-

edit :

"memory:"+path

works.