JDK 16 🥳 | Pattern matching for instanceof

What was my motivation for moving to JDK 16 and enjoying the new features that are delivered with JDK 16.

In this post we will have a look at pattern matching in Java.

Pattern matching allows common logic in a program, namely the conditional extraction of components from objects, to be expressed more concisely and safely.

All Java developers are familiar with the instanceof and cast idiom:

if (obj instanceof StringBuilder) {
  StringBuilder builder = (StringBuilder) obj;
  builder.append("Hello Medium")
}

We have three occurrences of the type StringBuilder (boilerplate code) and with this repetition we are exposed to create 🐛🐛🐛🐛🐛🐛🐛

A type pattern in JDK 16 consists of a predicate that specifies a type, along with a single pattern variable.This allows us to refactor the boilerplate code above to the following:

if (obj instanceof StringBuilder builder) {
  builder.append("Hello Medium")
}

More examples on this:

Tedious, Boilerplate code (< JDK 16)

public boolean equals(Object o) {
  if (!(o instanceof StringBuilder)) {
    return false;
  }
  StringBuilder other = (StringBuilder) o;
  return //Logic
}

Pattern matching (JDK 16)

public boolean equals(Object o) {
  return (o instanceof StringBuilder other)
  //Logic
}

Other features will be covered in the next posts 🎉🎉🥳🥳