Dave Musicant

Give students tips and resources to help them shift from one programming language to another.

cstt — Tue, 21 Jul 2015 18:13:25 +0000

Give students tips and resources to help them shift from one programming language to another. cstt Tue, 07/21/2015 - 11:13 Share Give students tips and resources to help them shift from one programming language to another. with Facebook Share Give students tips and resources to help them shift from one programming language to another. with Twitter

Show students how to use Google Search to find the syntax for a construct in a language.
- For example, if students want to know how to find the length of a string in Java, they should Google "string length method java example."
If students are moving from Python to Java, point them to Ken Lambert’s From Python to Java website, which provides an overview of differences between common programming concepts in Python and Java.
Note from the CS Teaching Tips Team: You can also direct students to StackOverflow, where users can publicly ask and answer programming questions, for another helpful resource. Check out Ellen Spertus’ tip about teaching students to use StackOverflow well!

Misconception: Students get confused with object-oriented programming in Python because function declarations explicitly take self as an argument, but function calls don’t use self as argument.

cstt — Tue, 21 Jul 2015 18:11:15 +0000

Misconception: Students get confused with object-oriented programming in Python because function declarations explicitly take self as an argument, but function calls don’t use self as argument. cstt Tue, 07/21/2015 - 11:11 Share Misconception: Students get confused with object-oriented programming in Python because function declarations explicitly take self as an argument, but function calls don’t use self as argument. with Facebook Share Misconception: Students get confused with object-oriented programming in Python because function declarations explicitly take self as an argument, but function calls don’t use self as argument. with Twitter

In the Python example below, notice how the method setSides has two formal parameters, but when we call it in main(), we only pass one argument.
If students are learning Object-Oriented Programming while transitioning between two languages, like Python and Java, this can be even more confusing.

In Java, self is an implicit argument when a method is defined. In Python, self is an explicit argument. In both Python and Java, self isn’t a required argument when the method/function is called.

As such, students struggle with reasoning about object oriented function declarations between Python and Java.

If students are moving from Python to Java, point them to Ken Lambert’s Python to Java resource for additional help.

Misconception: Students who first learn object-oriented programming in Python don’t realize they need to explicitly define instance variables in Java because this is done implicitly in Python.

cstt — Tue, 21 Jul 2015 18:08:45 +0000

Misconception: Students who first learn object-oriented programming in Python don’t realize they need to explicitly define instance variables in Java because this is done implicitly in Python. cstt Tue, 07/21/2015 - 11:08 Share Misconception: Students who first learn object-oriented programming in Python don’t realize they need to explicitly define instance variables in Java because this is done implicitly in Python. with Facebook Share Misconception: Students who first learn object-oriented programming in Python don’t realize they need to explicitly define instance variables in Java because this is done implicitly in Python. with Twitter

For example, in the Python code below, numSides is a data attribute (the Python equivalent of an instance variable).
- numSides does not require it’s own declaration, thus its use in self.numSides is sufficient for it’s existence.
  class Die:

Demonstrate manipulating primitives with operators before manipulating them with methods so students can understand the basics of primitives before using them in a more complicated way.

cstt — Tue, 21 Jul 2015 18:04:37 +0000

Demonstrate manipulating primitives with operators before manipulating them with methods so students can understand the basics of primitives before using them in a more complicated way. cstt Tue, 07/21/2015 - 11:04 Share Demonstrate manipulating primitives with operators before manipulating them with methods so students can understand the basics of primitives before using them in a more complicated way. with Facebook Share Demonstrate manipulating primitives with operators before manipulating them with methods so students can understand the basics of primitives before using them in a more complicated way. with Twitter

Use the following two examples to help students reason about primitives in Java.
- This first example provides a good introduction to manipulating primitives in Java using operators.
  int x = 42; int y = x; x++;
- Ask students what the values of x and y are now. (Answer: x=43 and y=42). A common misconception is that both x and y are incremented because y=x.
This second example uses method calls to change x and y.
- Wait to show students this example until they understand how primitives are manipulated by operators.
  public class Sample { public static void main (String [] args) { int x = 42; int y = x; Sample.myMethod(x); } public static myMethod(int x){ x = x + 1; } }
- x=42. Have students reason through how the method affects x and y.

Use dice to introduce instantiable classes in Java because it’s easier for novice students to create classes based on a familiar object.

cstt — Tue, 21 Jul 2015 18:00:37 +0000

Use dice to introduce instantiable classes in Java because it’s easier for novice students to create classes based on a familiar object. cstt Tue, 07/21/2015 - 11:00 Share Use dice to introduce instantiable classes in Java because it’s easier for novice students to create classes based on a familiar object. with Facebook Share Use dice to introduce instantiable classes in Java because it’s easier for novice students to create classes based on a familiar object. with Twitter

Create a Die class with one of its instance variables representing the number of sides the die object has.
Use the following example code to show students how to set instance variables:


public class Die {

    private int numSides;
    public void setSides(int sides) {

        numSides = sides;

}

}



public static void main(String[] args) {

    Die die1 = new Die();
    int x = 6;
    die1.setSides(x);

}

Note from CS Teaching Tips Team: To extend this analogy, have students create a method roll that returns the result of one roll of the die.

Misconception: Students have trouble distinguishing between instance variables and parameters in Java.

cstt — Tue, 21 Jul 2015 17:55:02 +0000

Misconception: Students have trouble distinguishing between instance variables and parameters in Java. cstt Tue, 07/21/2015 - 10:55 Share Misconception: Students have trouble distinguishing between instance variables and parameters in Java. with Facebook Share Misconception: Students have trouble distinguishing between instance variables and parameters in Java. with Twitter

You can remedy this by using different names for instance variables and parameters when providing sample code in Java.

Consider these two versions of the same method:

Version 1: The following code can confuse students because the instance variable and parameter represent different things, but they have the same name.
Version 2: In the following code, having different names for the instance variable and the parameter help differentiate the two.

Have students think about a reference to an object as a numeric memory address to help them understand how passing references works.

cstt — Tue, 21 Jul 2015 17:54:23 +0000

Have students think about a reference to an object as a numeric memory address to help them understand how passing references works. cstt Tue, 07/21/2015 - 10:54 Share Have students think about a reference to an object as a numeric memory address to help them understand how passing references works. with Facebook Share Have students think about a reference to an object as a numeric memory address to help them understand how passing references works. with Twitter

Teaching students this deeper model of memory can often make more sense to them than something more abstract.
As such, have students conceptualize a references as numeric memory addresses, like 0x9FFF0 and 0x3106eb.
- When an object is passed, its memory address is just being copied to the local variable being used.

Misconception: Students have trouble understanding the difference between checked and unchecked exceptions in Java.

cstt — Tue, 21 Jul 2015 17:50:37 +0000

Misconception: Students have trouble understanding the difference between checked and unchecked exceptions in Java. cstt Tue, 07/21/2015 - 10:50 Share Misconception: Students have trouble understanding the difference between checked and unchecked exceptions in Java. with Facebook Share Misconception: Students have trouble understanding the difference between checked and unchecked exceptions in Java. with Twitter

A checked exception is due to a bug outside the program’s control, for example a File Not Found Exception or an IO Exception.
An unchecked exception is due to a bug in the program, for example a Null Pointer Exception or Array Index Out Of Bound.

Have students who are transitioning from Python to Java explore the “From Python to Java” website to show them the differences between the two languages.

cstt — Mon, 29 Jun 2015 20:43:31 +0000

Have students who are transitioning from Python to Java explore the “From Python to Java” website to show them the differences between the two languages. cstt Mon, 06/29/2015 - 13:43 Share Have students who are transitioning from Python to Java explore the “From Python to Java” website to show them the differences between the two languages. with Facebook Share Have students who are transitioning from Python to Java explore the “From Python to Java” website to show them the differences between the two languages. with Twitter

The website provides an overview of differences between common programming concepts in Python and Java to assist students in their transition.
Check out the "From Python to Java" website!