Syntax Quiz 2, Step 13
Assignment:
Write an assignment statement to set instanceVar to this value.
My solution:
You've already written the expression
theParameter.length()
To assign a variable to this value, write
this.instanceVar = theParameter.length();
or
instanceVar = theParameter.length();
(The this. isn't required by Java, but I think it helps to
explain what's going on. instanceVar has no independent
existence except as part of a QuizClass object.
Since this is a QuizClass object,
this.instanceVar is really the complete reference.)
Common mistakes:
- Omitting the equals sign
- The equals sign is how Java knows that this is an assignment
statement, i.e. you're changing one variable to match another
expression.
- Reversing the positions of
instanceVar and
theParameter.length().
- The assignment statement in Java (and C and C++ and Basic) looks
superficially like an equation, but it actually has a very different
meaning: the thing on the left side of the equals sign is
changed to match the thing on the right side. So if you write
theParameter.length() = this.instanceVar;
you're trying to change the length of theParameter,
rather than copying that length into another variable.
- Omitting the semicolon.
- The assignment statement is a statement, and therefore ends with a
semicolon.
- Writing a double-equals sign, as in
this.instanceVar == theParameter.length();
- The double-equals sign in Java (and C and C++) asks whether
two things are the same. The assignment at hand is to make
them the same. This error is particularly insidious because it's
actually legal Java -- it won't produce a compiler error message -- but
neither will it do anything.
Stephen Bloch / sbloch@adelphi.edu