Buzz
When starting programming with Java, there are numerous concepts that you need to understand. These include classes, methods, exceptions, constructors, variables, and so on. To avoid being overwhelmed, it's best to learn each concept step by step. Today, Mytour will guide you on how to call a method in Java.
Steps to follow
You need to understand what a method is. In Java, a method is a collection of instructions grouped together to perform a specific task. Once a method is declared, we can call different parts of the code to execute its function. This is a practical way to reuse code. Below is an example of a simple method:
public static void methodName() {
System.out.println("This is a method");
}
Declare the method's access modifier. When declaring a method in Java, you need to specify which classes can access it. In the example above, the access modifier is set to "Public". There are three types of access modifiers you can declare for a method:
Public: By placing the "public" access modifier before the method name, we can call this method from anywhere.
Protected: The "protected" modifier allows the method to be called within the base class and subclasses only.
Private: If the access modifier is set to "private", the method can only be called within the class. This is the default or package-private access, meaning only classes in the same package can access this method.
Declare the class to which the method belongs. In the above example, the second keyword is "static", which indicates that the method belongs to the class itself and not to any instance or object of the class. A static method should be called using the class name: "ExampleClass.methodExample()".
If the "static" keyword is not used, the method can only be called through an object. For instance, if the class "ExampleObject" has a constructor (used to create objects), we can create a new object by entering "ExampleObject obj = new ExampleObject();" and call the method with: "obj.methodExample();".
Declare the return value. The return value defines the type of value that the method will return. In the above example, the word "void" indicates that the method does not return any value.
If you want a method to return a value, simply replace "void" with the data type (primitive or reference) of the object or primitive type you wish to return. Primitive data types include int, float, double, etc. Then, add "return" along with the object of that data type at the end of the method code.
When calling a method that returns a value, you can use the returned value. For example, if the method "someMethod()" returns an integer, you can assign that integer to a variable like: "int a = someMethod();".
Declare the method name. After specifying the classes that can access the method, the class to which the method belongs, and the return value, you need to name the method so that it can be called. To name the method, simply enter the method's name followed by parentheses, like "someMethod()" or "methodName()". Then, place all the method's instructions inside curly braces "{}".
Call the method. To call a method, simply enter the method's name along with parentheses in the line where you want it to be executed. Note: the method can only be called within a class that has access to it. Here is an example of a method being declared and called within a class:
public class className {
public static void methodName() {
System.out.println("This is a method");
}
public static void main(String[] args) {
methodName();
}
}
Add parameters to the method (if necessary). Some methods require parameters (such as an integer) or reference types (for example: object name). If a method requires parameters, simply enter the parameters between the parentheses following the method name. Here is an example of a method requiring an integer parameter: "someMethod(int a)" or similar. A method using reference types will look like: "someMethod(Object obj)" or similar.
To call a method with parameters, simply include the parameters within the parentheses following the method name. For example, 'someMethod(5)' or 'someMethod(n)' where 'n' is an integer. If the method requires a reference to an object, pass the object name in the parentheses. For instance, 'someMethod(4, thing)'.
Methods can also accept multiple parameters, separated by commas. Here is an example of a method designed to add two integers and return the sum. When invoked, the two integers are added together. After the program executes, you will get the output 'The sum of A and B is 50':
```java
public class myClass {
public static void sum(int a, int b) {
int c = a + b;
System.out.println("The sum of A and B is " + c);
}
public static void main(String[] args) {
sum(20, 30);
}
}
```
Advice
After calling a method that returns a value, you can immediately call another method based on the returned value. For example, if the method 'getObject()' returns an object, and the 'Object' class contains a non-static 'toString' method that returns the value 'Object' when called, you can retrieve this 'String' value from the object returned by 'getObject()' in a single line like this: 'String str = getObject().toString();'.
Warning
Note about abstract classes and methods: Abstract methods cannot be used until they are implemented by another class. This is because abstract methods do not have any implementation code. Abstract classes serve as a framework or blueprint for other classes to follow.
