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How to call a method in Java
In this post, we will learn how to call a method in Java. This is a useful “chunk” of code that you can call from anywhere else in your program, thus preventing you from needing to write out the same lines of code over and over.
By designing code this way, developers can create far more modular and portable programs and save significant time typing out code.
How to call a method in Java – the basics
To call a method in Java, you type the method’s name, followed by brackets.
For example, the following will call a method called “helloMethod()”:
helloMethod();In order for this to work though, we first need to create our helloMethod() method. We can see what helloMethod might look like, here:
public static void helloMethod() {
System.out.println("Hello world!");
}This code simply prints “Hello world!” to the screen. Therefore, any time we write helloMethod(); in our code, it will show that message to the screen.
If you ever want to change the message being displayed, you will only have to change it once – rather than every single time you used it in the code.
How to create methods in Java
Let’s rewind a moment and take a closer look at the method we created. Why does it look the way it does?
To build a method, we use a number of statements to define that method. In the previous example:
- Public – Means that the method is accessible to other classes outside of this one
- Static – Means that the method belongs to the class and not the instance of the class
- Void – Means that the method does not return a value
If none of that makes any sense to you, don’t worry! Most new developers will be able to use “public static void” for the majority of their methods and won’t have to worry. That said, we’ll address two of these phrases in the coming sections.
It is considered good practice to name Java methods using “camel case.” As we aren’t allowed spaces, camel case gets around this by capitalizing every word except the first one. Methods should generally be verbs (though I have bent that rule here!).
See also: An introduction to Java syntax for Android development
After we’ve named our method, we use brackets in order to add any arguments. An argument is a variable that we wish to pass from one method to another. Variables are values represented by words. Again, if that’s confusing, then just adding two closed brackets is fine.
You then open the code block using “{“. All the code that follows should be indented, and will be part of the method and will run when you call that method.
How to use arguments when calling a method in Java
As mentioned, we can place arguments inside of the brackets when defining our methods. This allows us to pass variables, and therefore values, between methods.
For example, a “String” is a type of variable that holds alphanumeric characters. We create a string by using the word “String” followed by the name.
Now, whenever we call that method, we need to add the value we want to use in the brackets.
helloClass.helloMethod("Hello there!");
public static void helloMethod(String helloMessage) {
System.out.println(helloMessage);
}How to call a method from outside the class
A public method is a method that can be called from outside your class. To do this, you use the following syntax:
nameOfClass.nameOfMethod(arguments)
For example:
class Main {
public static void main(String[] args) {
helloClass.helloMethod();
}
}
class helloClass {
public static void helloMethod() {
System.out.println("Hello world!");
}
}However, if we wanted to prevent this from working, we would simply replace the word “public” with the word “private”.
How to return values
Finally, we can return specific values from our methods. Let’s see how this might be used.
Let’s say we decide we want the method to provide our greeting but not display it onto the screen. Thus, we might make the method return a string. To do this, we change the word “void” for the type of variable we want to return, and we add “return value” at the end of the method.
This changes how we call a method in Java, because we can simply insert the name of the method in-line in our code, as though it were a variable:
class Main {
public static void main(String[] args) {
System.out.println(helloMethod());
}
public static String helloMethod() {
return "Hello there!";
}
}If you’re still wondering what all that “static” stuff is about, then we recommend reading up on classes and objects over at the official Java Documentation from Oracle.
Alternatively, why not check out our list of the best places to learn Java. There you will learn about objects, classes, and much more besides!