Java Class Methods

Usually in Java, we declare methods inside the class, and they are used to perform certain actions as we have seen before in Java Methods chapter.

Example

In the below example, we create a method print() and in the main class we called the method using the same method name followed by parentheses () and the semicolon ;

public class classMethod {
       static void print(){
              System.out.println("Welcome to SparkDatabox");
       }
      
       public static void main(String args[]){
              print();
       }
}

Output

Welcome to SparkDatabox

 

Static or Public

In Java, we either use static or public attributes and methods.

In the above example, we created a static method, which means that it can be accessed without creating an object of the class unlike public, which can only be accessed by objects.

Example

The below example demonstrates between static and public methods:

public class StaticvsPublic {
       static void staticMethod(){
              System.out.println("Static methods can be called without creating objects");
       }
      
       public void publicMethod(){
              System.out.println("Public methods must be called by creating objects");
       }

       public static void main(String args[]){
              staticMethod ();
              StaticvsPublic myObj = new StaticvsPublic();
              myObj.publicMethod();
       }
}

 

Output

Static methods can be called without creating objects
Public methods must be called by creating objects

Access Methods with an Object

The public methods can be accessed with an object with the dot operator (.)

Example

public class Person {
       public void name(String name){
              System.out.println("Name : " +name);
       }
       public void designation() {
              System.out.println("Software Engineer");
       }

       public static void main (String args[]){
              Person emp = new Person();
              emp.name("John");
              emp.designation();
       }
}

Output

Name : John
Software Engineer

Example – Explanation

• We create a custom class Person with the class keyword.
• We create methods name() and designation() in the class Person.
• Both the methods, prints some text when they are called from the main method.
• The name method accepts the person name which is a String and prints in the function.
• In order to use the Person class, we create a emp object for the class Person.
• Then, go to the main() method, which is a built-in Java method that runs your program.
•  By using the new keyword, we create a Person object with the name emp.
• Then, we call the methods name() and designation() using the emp object, and run the program using the name of the object(emp) followed by dot (.), followed by the name of the method (name and designation)and it is followed by the parentheses. In the method name, we pass the String parameter “John” and it is used in the method definition.
  

Note: The dot (.) is used to access the object’s attributes and methods.

 

Using Multiple Classes

Usually we practice to create an object of a class and access it in another class. Remember that the name of the java class should be same as file name.

Example:

We create two files under the same directory / folder:

• EmployeeDetails.java
• EmpMain.java
  
  

EmployeeDetails.java

package practices;

public class EmployeeDetails {
       public void name(String name){
              System.out.println("Employee name : "+name);
       }
       public void employee_id(int emp_id){
              System.out.println("Employee id : "+emp_id);
       }
}

EmpMain.java

package practices;
 
public class EmpMain {
       public static void main(String args[]){
              EmployeeDetails emp = new EmployeeDetails();
              emp.name("Eric");
              emp.employee_id(456);
       }
}

Output

Compile both the files and below is the output :

Employee name : Eric
Employee id : 456