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Java objects and references, visualized

A variable that holds an object holds a reference to it, not the object itself. Step through the program and watch two variables share one object while a third has its own copy.

Source

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Call stack

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What to watch

  • Point b = a copies the reference, so a and b point to the same object.
  • moveRight changes the object through its parameter, and the change shows up through a as well.
  • a == c is false even though the values match, because == compares references, not contents.

Try changing it

  • Set b to a new Point inside moveRight and see whether a changes.
  • Add an equals method to Point and compare a.equals(c).

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