Helping understand different notions of equality

equality.gs

// gosu

var x = ...
var y = ...

if( x == y ) {
   print("x and y are value equal, including null")
}

if( x === y ) { // note, triple equals!
   print("x and y are references equal, including null")
}

if( x.equals( y ) ) {
  print("x and y are value equal, unless x is null, in which case there is an NPE in the condition above.") 
}
        
// java
Object x = ...
Object y = ...

if( x == y ) {
   print("x and y are references equal, including null")
}

if( x.equals( y ) ) {
  print("x and y are value equal, unless x is null, in which case there is an NPE in the condition above.") 
}

// correct equality test in java
if( (x == y) || (x != null && x.equals(y)) ) {
  print("x and y are value equal and this is null save") 
}

// There is a helper for the above code:
if( java.util.Objects.equals(x, y) ) {
  print("x and y are value equal and this is null save") 
}

// now you can see why gosu is so much better than java... :)