Flash cards
Review the key moves
What is the main idea behind Java Class Methods?
Lesson checks
Practice each idea before moving on
Short Mimo-style checks built from this lesson's code, terms, and sequence.
Which statement best captures the main point of this lesson?
Complete the missing token from the example code.
public ___ Main {Put the learning moves in the order that makes the concept easiest to apply.
You learned from the Java Methods chapter that methods are declared within a class, and that they are used to perform certain actions:
Create a method named myMethod() in Main:
public class Main {
static void myMethod() {
System.out.println("Hello World!");
}
}myMethod() prints a text (the action), when it is called . To call a method, write the method's name followed by two parentheses () and a semicolon ;
mainAccess Methods With an Object
myCarExample explained
1) We created a custom Main class with the class keyword.
2) We created the fullThrottle() and speed() methods in the Main class.
3) The fullThrottle() method and the speed() method will print out some text, when they are called.
4) The speed() method accepts an int parameter called maxSpeed - we will use this in 8) .
5) In order to use the Main class and its methods, we need to create an object of the Main Class.
6) Then, go to the main() method, which you know by now is a built-in Java method that runs your program (any code inside main is executed).
7) By using the new keyword we created an object with the name myCar .
8) Then, we call the fullThrottle() and speed() methods on the myCar object, and run the program using the name of the object ( myCar ), followed by a dot ( . ), followed by the name of the method ( fullThrottle(); and speed(200); ). Notice that we add an int parameter of 200 inside the speed() method.
Remember that..
The dot ( . ) is used to access the object's attributes and methods.
To call a method in Java, write the method name followed by a set of parentheses () , followed by a semicolon ( ; ).
A class must have a matching filename ( Main and Main.java ).
Using Multiple Classes
Like we specified in the Classes chapter , it is a good practice to create an object of a class and access it in another class.
Remember that the name of the java file should match the class name. In this example, we have created two files in the same directory:
- Main.java
- Second.java
public class Main {
public void fullThrottle() {
System.out.println("The car is going as fast as it can!");
}
public void speed(int maxSpeed) {
System.out.println("Max speed is: " + maxSpeed);
}
}class Second {
public static void main(String[] args) {
Main myCar = new Main(); // Create a myCar object
myCar.fullThrottle(); // Call the fullThrottle() method
myCar.speed(200); // Call the speed() method
}
}When both files have been compiled
C:\Users\
Your Name
>javac Main.java
C:\Users\
Your Name
>javac Second.javaRun the Second.java file:
C:\Users\
Your Name
>java SecondAnd the output will be
The car is going as fast as it can!
Max speed is: 200