Java - OOP - Modifiers - Public

Java modifiers are keywords that are used to control the access level and other properties of classes, variables, and methods. The public modifier is one of the access modifiers in Java and is used to make the associated class, variable, or method accessible from anywhere in the program.

When a class, variable, or method is declared with the public modifier, it can be accessed from any other class or package in the program. This makes it a very powerful modifier to use, as it allows for maximum flexibility in the use of classes, variables, and methods within a program.

Here's an example of using the public modifier with a class:

public class MyClass {
  // class contents go here
}

In this example, the MyClass class is declared as public, meaning that it can be accessed from anywhere in the program. Any other class in the program can create an object of type MyClass and call its methods or access its properties.

Here's an example of using the public modifier with a variable:

public int myVariable = 42;

In this example, the myVariable variable is declared as public, meaning that it can be accessed from anywhere in the program. Any other class in the program can access the value of myVariable and use it in their own calculations.

Here's an example of using the public modifier with a method:

public void myMethod() {
  // method contents go here
}

In this example, the myMethod method is declared as public, meaning that it can be accessed from anywhere in the program. Any other class in the program can call myMethod and execute the code within it.

Overall, the public modifier is a powerful tool in Java programming, as it allows for maximum flexibility and access within a program. It should be used judiciously, however, as it can also make a program more difficult to understand and maintain if overused.

public class Person {
    public String name;
    public int age;
    
    public Person(String name, int age) {
        this.name = name;
        this.age = age;
    }
    
    public void introduce() {
        System.out.println("Hi, my name is " + name + " and I am " + age + " years old.");
    }
}

public class Main {
    public static void main(String[] args) {
        Person person = new Person("John", 25);
        person.introduce();
    }
}

In this example, we have a Person class with name and age attributes, as well as a constructor and an introduce() method. The public modifier is used to make these attributes, constructor, and method accessible from other classes.

In the Main class, we create a new Person object with the name "John" and age 25 using the constructor, and then call the introduce() method on that object, which will print out "Hi, my name is John and I am 25 years old."

Without the public modifier, these attributes, constructor, and method would only be accessible within the Person class and not from any other class.