@Override
  public String getString() {
    return this.string;
  }
@Test
  public void testGetString() {
    ValueString vs = new ValueString( "Boden" );

    assertEquals( "Boden", vs.getString() );
    assertEquals( 0.0, vs.getNumber(), 0.0D );
    assertNull( vs.getDate() ); // will fail parsing
    assertEquals( false, vs.getBoolean() );
    assertEquals( 0, vs.getInteger() );
    try {
      vs.getBigNumber();
      fail( "Expected a NumberFormatException" );
    } catch ( NumberFormatException ex ) {
      vs = null;
    }
  }