[usth/ICT2.2] Object Oriented Programming

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+# String Concatenation
+
+To quote the [official Java documentation](https://docs.oracle.com/javase/8/docs/api/java/lang/String.html):
+
+> The Java language provides special support for the string concatenation
+> operator (`+`), and for conversion of other objects to strings.  [...]
+> String conversions are implemented through the method `toString`, defined
+> by Object and inherited by all classes in Java.
+
+Thus the numbers (e.g. 2, 2 + 3 = 5) are converted to their strings
+representations ("2", "5") and concatenated to the string.  Since `+` is
+operated from left to right,
+
+    2 + 3 + "bc" = 5 + "bc" = "5" + "bc" = "5bc"
+    "bc" + 2 + 3 = "bc" + "2" + 3 = "bc2" + 3 = "bc2" + "3" = "bc23"