can you put a class in a class java code example

Example 1: using class in java

public class HelloWorld {
  public static void main(String[] args) {
    
    // how to use class in java
    class User{
    	
    	int score;
    }
    
    User dave = new User();
    
    dave.score = 20;
    
    System.out.println(dave.score);
    
 
  }
}

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());