Method Parameters: Fill in the Blanks

1.      The following program is to print the number of characters in the string:

class HowLong
{
  public static void main ( String[] args )
  {
    String str = "Count Carefully!" ;
    int len =  .  ;
    System.out.println( "Number of characters: " + len );
  }
}

2.      Remember that the + operator takes two string objects and returns a new object that contains the concatenated characters of the first two objects. In other words, the first two objects are not changed, and a third object is created.

The following program is to concatenate the two named strings and print out the length of the result:

class HowLongTwo
{
  public static void main ( String[] args )
  {
    String str1 = "New strings " ;
    String str2 = "for old." ;

    int len = (  +  ) .  ;
    System.out.println( "Number of characters: " + len );
  }
}

3.      Another way to create a string object that contains the concatenated characters of two other strings is by using the concat(String st) method. This method takes a parameter, which is the second string, whose characters are to be joined to the string whose method is running.

The following program is to do the same thing as the previous program:

class SameAgain
{
  public static void main ( String[] args )
  {
    String str1 = "New strings " ;
    String str2 = "for old." ;

    String str3 = str1. (  )  ;
    System.out.println( "Number of characters: " + str3. );
  }
}

4.      The following program draws a line on a graphics area between pointA and pointB. (You have not seen several of the features of this program before, but you can ignore them and look only at the Point objects.) Fill in the blanks so that the program next draws a line parallel to the first line, but moved 10 positions to the right.

class DrawLines extends Applet
{
  public void paint ( Graphics graph )
  {
    Point pointA = new Point( 10, 20 );
    Point pointB = new Point( 30, 70 );
    graph.drawLine( pointA.x, pointA.y, pointB.x, pointB.y );

    pointA.move( , 20 );
    pointB.move( , 70 );

    graph.drawLine( pointA.x, pointA.y, pointB.x, pointB.y );

  }
}

5.      In general, a conversion between two data types is not automatically performed if there is the risk of a of information.

6.      In each of the following situations, the compiler will automatically convert from the type of the actual parameter in the parameter list to the type of parameter that the method requires:

• Convert from an integer type to another integer type with bits.
• Convert from a floating point type to another floating point type with bits.
• Convert from an integer type to a floating point type with number of bits (although this may result in loss of precision.)
• Convert from an integer type to a floating point type with bits (this will not result in loss of precision.)

7.      In each of the following situations, the compiler will NOT automatically convert from the type of the actual parameter in the parameter list to the type of parameter that the method requires:

• Convert from an integer type to another integer type with bits.
• Convert from a floating point type to another floating point type with bits.
• Convert from a floating point type to an integer type with number of bits.

8.      A is used to ask the compiler to perform a conversion that it would not automatically do.

9.      The programmer knows that the following program will work correctly. Fill in the blank to inform the compiler that it is OK to perform the conversion. Recall that most Math methods require double arguments.

class SinEg
{
  public static void main ( String[] args )
  {
    float angle = 2.56;

    System.out.println( "Sine of angle is " + Math.sin( () angle ) );
  }
}

10.      In the following situation, what can be said of the values of X and Y after the doSomething() method has returned?

. . .
int X = 41;
int Y = -12;
. . .
someObject.doSomething( X, Y );
. . .

The values of X and Y will be as before the method call, no matter what object and method are involved.