Methods
- Java course
- Intermediate
- Lesson 3/116
- 4 min
Learn methods and this inside a class.
Methods
A method is a code block that defines a class's behavior. A method has a name, a parameter list, a return type and a body. The body sits between curly braces.
Example: void greet() { System.out.println("Hello"); }. Here void is the return type (returns nothing), greet is the method name, empty parentheses mean no parameters. A method is defined once and called on an instance as object.method(). Parameterized methods take values in parentheses.
The this keyword
Inside a method body, this refers to the instance on which the method was called. It is used to distinguish a field from a parameter with the same name. When a parameter shadows a field, this.field accesses the instance's field.
Example: void setName(String name) { this.name = name; }. Here the parameter name and the field name share the same name. this.name means the instance's field, name means the parameter. Without this, the assignment would target the parameter itself; the field would not change.
Practice Add a method to the Greeter class
Define a class named Greeter. Add a String name field and a void greet() method. In the method body write System.out.println("Hello " + name);. In main create a Greeter instance, assign a value to name and call the greet method.
Starter code
// Define the Greeter class
// Add a String name field and a greet method
// Instantiate and call greet in mainSample solution
class Greeter {
String name;
void greet() {
System.out.println("Hello " + name);
}
public static void main(String[] args) {
Greeter g = new Greeter();
g.name = "World";
g.greet();
}
}Expected output
Hello World
Questions and answers
Review the lesson questions together with their answers. To test yourself, solve the lesson interactively.
1 What does void mean in a method definition?
- The method returns no value Correct answer
- The method returns a string
- The method is hidden
- The method is static
Explanation: The void return type means the method returns no value.
2 Complete the method call
class Greeter {
void greet() {
System.out.println("Merhaba");
}
public static void main(String[] args) {
Greeter g = new Greeter();
g____;
}
}class Greeter {
void greet() {
System.out.println("Merhaba");
}
public static void main(String[] args) {
Greeter g = new Greeter();
g.greet();
}
}Explanation: The method is called with .greet() on the instance.
3 Match the method parts
| Term | Meaning |
|---|---|
void |
Return type |
greet |
Method name |
() |
Parameter list |
{ } |
Body |