public class Homework {

    public static void main(String[] args) {
        // TODO Auto-generated method stub
        int n = 4;
        int start = 1;
        int end = n*(n+1);
        for(int i=0; i<n; i++){
            for(int j=i; j>0; j--)
                System.out.print("--");
            for(int j=0; j<n-i; j++)
                System.out.print(start++ +"*");
            for(int j=0; j<n-i; j++){
                if(j == n-i-1)
                    System.out.print( (end - (n-j)+1) );
                else
                    System.out.print( (end - (n-j)+1) + "*" );
            }
            end = end - (n- i)+1;
            System.out.println();
        }
    }
}

Mari menjadi ganas

public static void homework(int n)
    {
        for(int i=1;i<=n;i++)
        {
            for(int j=1;j<i;j++)
                System.out.print("--");
                                
            for(int j=(2*n-i+2)*(i-1)/2+1;j<(2*n-i+1)*i/2+1;j++)
                System.out.print(j+"*");
    
            for(int j=(((1+n-i)*(n-i))/2+(n*(n+1))/2+1);j<=(((2+n-i)*(n-i+1)/2)+(n*(n+1)/2));j++)
            {
                if(j==((2+n-i)*(n-i+1)/2+n*(n+1)/2))
                    System.out.print(j);
                else
                    System.out.print(j+"*");
            }

            System.out.println();
        }
        
    }