Need some help with a compiler issue

[eindoofus]

I was able to compile some code fine on ideone.com with only one import statement but when I try to compile the files on my local computer I get some errors. I'm not sure if I'm doing something wrong.

Here is some more info:

I copy and pasted the following two classes into the ideone.com web-based compiler and I didn't run into any problems upon compiling:

/****************************************
*****************************************/
/**
 * A class for numeric progressions.
 */

import java.math.BigInteger;
// public class Progression {  CHANGED IN ORDER TO COMPILE ON IDEONE.COM
class Progression {
  /** First value of the progression.  */
  protected BigInteger first;

  /** Current value of the progression.  */
  protected BigInteger cur;

  /** Default constructor.  */
  Progression() {
    cur = first = BigInteger.ZERO;
  }

  /** Resets the progression to the first value.
   * 
   * @return first value
   */
  protected BigInteger firstValue() {
    cur = first;
    return cur;
  }

  /** Advances the progression to the next value.
   *
   * @return next value of the progression
   */
  protected BigInteger nextValue() {
    
    cur = cur.add(BigInteger.ONE);
    return cur; // default next value
  }

  /** Prints the first n values of the progression.
   * 
   * @param n number of values to print
   */
  public void printProgression(int n) {
    System.out.print(firstValue());
    for (int i = 2; i <= n; i++) 
      System.out.print(" " + nextValue());
    System.out.println(); // ends the line
  }

   
}

/****************************************
*****************************************/
/**
 * Arithmetic progression.
 */


class ArithProgression extends Progression {

  /** Increment. */
  protected BigInteger inc;

  // Inherits variables first and cur.

  /** Default constructor setting a unit increment. */
  ArithProgression() {
    this(BigInteger.ONE);
  }

  /** Parametric constructor providing the increment. */
  ArithProgression(BigInteger increment) {
    inc = increment; 
  }

  /** Advances the progression by adding the increment to the current value.
   * 
   * @return next value of the progression
   */
  protected BigInteger nextValue() {
    cur = cur.add(inc);
    return cur;
  }

  //  Inherits methods firstValue() and printProgression(int).
}

However after I pasted the code into two java files on my local computer and tried to compile them:

Progression.java

/**
 * A class for numeric progressions.
 */

import java.math.BigInteger;
// public class Progression {  CHANGED IN ORDER TO COMPILE ON IDEONE.COM
class Progression {
  /** First value of the progression.  */
  protected BigInteger first;

  /** Current value of the progression.  */
  protected BigInteger cur;

  /** Default constructor.  */
  Progression() {
    cur = first = BigInteger.ZERO;
  }

  /** Resets the progression to the first value.
   * 
   * @return first value
   */
  protected BigInteger firstValue() {
    cur = first;
    return cur;
  }

  /** Advances the progression to the next value.
   *
   * @return next value of the progression
   */
  protected BigInteger nextValue() {
    
    cur = cur.add(BigInteger.ONE);
    return cur; // default next value
  }

  /** Prints the first n values of the progression.
   * 
   * @param n number of values to print
   */
  public void printProgression(int n) {
    System.out.print(firstValue());
    for (int i = 2; i <= n; i++) 
      System.out.print(" " + nextValue());
    System.out.println(); // ends the line
  }

   
}

ArithProgression.java

/**
 * Arithmetic progression.
 */


class ArithProgression extends Progression {

  /** Increment. */
  protected BigInteger inc;

  // Inherits variables first and cur.

  /** Default constructor setting a unit increment. */
  ArithProgression() {
    this(BigInteger.ONE);
  }

  /** Parametric constructor providing the increment. */
  ArithProgression(BigInteger increment) {
    inc = increment; 
  }

  /** Advances the progression by adding the increment to the current value.
   * 
   * @return next value of the progression
   */
  protected BigInteger nextValue() {
    cur = cur.add(inc);
    return cur;
  }

  //  Inherits methods firstValue() and printProgression(int).
}

"javac Progression.java" compiles fine but "javac ArtihProgression.java" spits out the following problems:

ArithProgression.java:13: cannot find symbol
symbol : class BigInteger
location: class ArithProgression
protected BigInteger inc;
^
ArithProgression.java:23: cannot find symbol
symbol : class BigInteger
location: class ArithProgression
ArithProgression(BigInteger increment) {
^
ArithProgression.java:31: cannot find symbol
symbol : class BigInteger
location: class ArithProgression
protected BigInteger nextValue() {
^
ArithProgression.java:19: cannot find symbol
symbol : variable BigInteger
location: class ArithProgression
this(BigInteger.ONE);
^
4 errors

Am I compiling this wrong or do I have to put "import java.math.BigInteger;" into every file that extends "Progression.java" as well?

[dlorde]

You need to put the class import into every file that mentions the class.

The file is a 'compilation unit' and import declarations apply within the scope of a compilation unit. See Import Declaration Scope and Import Declarations.

If you understand what you're doing, you're not learning anything...
Anon.