Hola java

public class hola
{
public static void main (String[] ar)
{
System.out.println ("hola mundo java ");
System.out.println ("oscar javier pineda duarte ");
System.out.println("edad 16años ");
System.out.println("fundacion universitaria san martin ");
System.out.println("codigo:191013112008 ");

}

}

import java.util.Scanner;
public class volumen {
publicstatic void main (String[] ar)
{
Scanner teclado = new Scanner (System.in);
float a,b,c,v ;
System.out.print("ingrese la base");
a=teclado.nextFloat();System.out.print("ingrese la altura ");
b=teclado.nextFloat();
System.out.print("ingrese la profundidad ");
c=teclado.nextFloat();
v=a*b*c;
System.out.println("EL VOLUMEN DE LA CAJAES:"+v);
System.out.println ("oscar javier pineda duarte");
System.out.println("primer semestre");
System.out.println("fundacion universitaria san martin ");System.out.println("codigo:191013112008 ");
System.out.println ("lab de programacion 1 " );
}
}

import java.util.Scanner;
public class tablademultiplicar
{
public static void main (String[] ar)
{Scanner teclado = new Scanner (System.in);
int a,b;
System.out.print("digite el numero de la tabla que quiere ver");
a=teclado.nextInt();
b=a*1;
System.out.println(a+"*1="+b);b=a*2;
System.out.println(a+"*2="+b);
b=a*3;
System.out.println(a+"*3="+b);
b=a*4;
System.out.println(a+"*4="+b);
b=a*5;
System.out.println(a+"*5="+b);b=a*6;
System.out.println(a+"*6="+b);
b=a*7;
System.out.println(a+"*7="+b);
b=a*8;
System.out.println(a+"*8="+b);
b=a*9;
System.out.println(a+"*9="+b);b=a*10;
System.out.println(a+"*10="+b);
System.out.println ("oscar javier pineda duarte");
System.out.println("primer semestre");
System.out.println("fundacion universitaria...