why do we use class in java code example

Example 1: java class

public class Lightsaber {
  // properties
  private boolean isOn;
  private Color color;
  
  // constructor
  public Lightsaber(Color color) {
    this.isOn = false;
    this.color = color;
  }
  
  // getters
  public Color getColor() {
    return color;
  }
  public boolean getOnStatus() {
    return isOn;
  }
  
  // setters
  public void turnOn() {
    isOn = true;
  }
  public void turnOff() {
    isOn = false;
  }
}



// Implementation in main method:
public class test {
  public static void main(String[] args) {
    Lightsaber yoda = new Lightsaber(green);
    yoda.turnOn();
  }
}

Example 2: using class in java

class Number {
    	
    	int number;
    	
    	// square numbers
    	public boolean isSquare(){
    		
    		double squareRoot = Math.sqrt(number);
    		
    		
    		if(squareRoot == Math.floor(squareRoot))
    		{
    			return true;
    		} else {
    			return false;
    		}
    		
    	}
    	
    	// triangular numbers
    	public boolean isTriangular(){
    		
    		int x = 1;
    		
    		int triangularNumber = 1;
    		
    		while(triangularNumber < number){
    			
    			x++;
    			triangularNumber = triangularNumber + x;
    			
    		}
    		
    		if(triangularNumber == number){
    			return true;
    		} else {
    			return false;
    		}
    	}
    }
    
    // testing 
    Number myNumber = new Number();
    myNumber.number = 16;
    
    System.out.println(myNumber.isSquare());

Example 3: using class in java

public class HelloWorld {
  public static void main(String[] args) {
   
   
   class Number{
   
   	int number;
   
   	public boolean isPos(){
   		if(number > 0){
   			return true;
   		} else {
   			return false;
   		}
   		
   	}
   }
   
   Number myNumber = new Number();
   
   myNumber.number = 7;
   
   if(myNumber.isPos()){
   	System.out.println(myNumber.number + " is positive!!!");
   } else {
   	System.out.println(myNumber.number + " is not positive!!!");
   }
   
  }
}