See https://en.wikipedia.org/wiki/Tagged_union

In languages influenced by ML (like contemporary Java!) it is common in compiler work in that you might have an AST or similar kind of structure and you end up writing a lot of functions that use pattern matching like

   switch(node) {
      type1(a,b) -> whatever(a,b)
      type2(c) -> process(c)
   }

to implement various "functions" such as rewriting the AST into bytecode, building a symbol table, or something. In some cases you could turn this inside out and put a bunch of methods on a bunch of classes that do various things for each kind of node but if you use pattern matching you can neatly group together all the code that does the same thing to all the different objects rather than forcing that code to be spread out on a bunch of different objects.