Intro to Java with Greenfoot

Unit 3: Methods, Worlds, and Constructors

The heaviest unit, and the one that buys the most later. Writing methods, parameters and return values, the World class, constructors, and instance variables, which is where a game finally learns to remember a score.

• 9 lessons
• about 4 hours
• Unit 3 of 6

Lessons in this unit

• 3.1 Why Write a Method · 25 min
• 3.2 Writing a void Method · 30 min
• 3.3 Methods with Parameters · 30 min
• 3.4 Return Types · 30 min
• 3.5 The World Subclass · 25 min
• 3.6 The World Constructor · 25 min
• 3.7 The prepare() Method · 30 min
• 3.8 Instance Variables · 35 min
• 3.9 The Actor Constructor · 30 min

Support pages for this unit

These cover the problems that come up during these lessons. Students can open them freely; doing so is not tracked and is never counted against them.

• I wrote a method and nothing happens
• My score always stays at zero
• My actor jumps across the screen
• Java error: constructor cannot be applied to given types
• How to show a score on screen
• How to set up the opening scene