how do i call methods through classes in java code example

Example 1: how to call a function from a class java

public class Classroom {
	 private String teacherName;
	
  	 public Classroom(String teacherName){
       this.teacherName = teacherName;
     }
  
  	 public String getTeacherName() {
        return teacherName;
     } 
}

public static void main(String[] args){
	Classroom firstGrade = new Classroom("John");
    /*Once you type the 'firstGrade.' your IDE most likely 
	will show all the functions it can acess*/
    firstGrade.getTeacherName();
}

Example 2: java classes and methods

import java.lang.Math;
import java.util.Scanner;

public class HelloWorld {
  public static void main(String[] args) {
    class ResultNumberShape {

            double number;

            public boolean isSquare(double number) {

                double result = Math.sqrt(number);
                return ((result - Math.floor(result)) == 0);

            }
        }

        ResultNumberShape checkNumber = new ResultNumberShape();

        System.out.println("Enter any number:");
        Scanner scanner = new Scanner(System.in);
        double num = scanner.nextDouble();

        scanner.close();

        if (checkNumber.isSquare(num)) {
            System.out.println(num + " is a sqaure number!");
        } else {
            System.out.println(num + " is not a square!");
        }
    
  }
}