ch3-Programs

Chapter_3     ch3-Hello                                                                                   ch3-Autoboxing 

Contents:

Exercise_3-2     Exercises_3-3,4 

Exercise 3-2     TCS, p. 85

Exercise 3-2. Find the code fragments involving ATypeName and turn them into a program that compiles and runs.

ATypeName.cs     TCS, p. 55

public class ATypeName

{

  public static void Main()

  {

    ATypeName a = new ATypeName();

  }

}

/*

mcs ATypeName.cs

// 1 warning: var 'a' value never used

mono ATypeName.exe

*/

Note:

public class ATypeName {}

will not compile in C#, although it does compile (but does not run) in Java (see Exercise_3-3 on the Thinking_in_Java_site.)

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Exercises 3-3, 3-4     TCS, p. 85

Exercise 3-3. Turn the DataOnly code fragments into a program that compiles and runs.

Exercise 3-4. Modify Exercise 3-3 so that the values of the data in DataOnly are assigned to and printed in Main().

DataOnly.cs     TCS, p. 56

public class DataOnly

{

  public int i;

  public float f;

  public bool b;

  private string s;

  public static void Main()

  {

    DataOnly data = new DataOnly();

    System.Console.WriteLine("uninitialized int: " + data.i);

    System.Console.WriteLine("uninitialized float: " + data.f);

    System.Console.WriteLine("uninitialized boolean: " + data.b);

    System.Console.WriteLine("uninitialized string: " + data.s);

    // Main() is part of DataOnly, so it has access to its private fields:

    data.i = 47;

    data.f = 1.1f; // 1.1 is implicitly double (compile error)

    data.b = false; // true

    data.s = "classified";

    System.Console.WriteLine("int field: " + data.i);

    System.Console.WriteLine("float field: " + data.f);

    System.Console.WriteLine("boolean field: " + data.b);

    System.Console.WriteLine("string field: " + data.s);

  }

}

/*

mcs DataOnly.cs

mono DataOnly.exe

uninitialized int: 0

uninitialized float: 0

uninitialized boolean: False

uninitialized string: 

int field: 47

float field: 1.1

boolean field: False

string field: classified

*/

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TestDataOnly.cs

public class TestDataOnly

{

  class DataOnly // inner class

  {

    public int i;

    public float f;

    public bool b;

    private string s;

  }

  public static void Main()

  {

    DataOnly data = new DataOnly();

    System.Console.WriteLine("uninitialized int: " + data.i);

    System.Console.WriteLine("uninitialized float: " + data.f);

    System.Console.WriteLine("uninitialized boolean: " + data.b);

    // Main() is not part of DataOnly, so it cannot access its private field:

    // System.Console.WriteLine("uninitialized string: " + data.s); // compile error

    data.i = 47;

    data.f = 1.1f; // 1.1 is implicitly double (compile error)

    data.b = false; // true

    // data.s = "classified"; // compile error

    System.Console.WriteLine("int field: " + data.i);

    System.Console.WriteLine("float field: " + data.f);

    System.Console.WriteLine("boolean field: " + data.b);

    // System.Console.WriteLine("string field: " + data.s); // compile error

  }

}

/*

mcs TestDataOnly.cs

// 1 warning: The private field `TestDataOnly.DataOnly.s' is never used

mono TestDataOnly.exe

uninitialized int: 0

uninitialized float: 0

uninitialized boolean: False

int field: 47

float field: 1.1

boolean field: False

*/

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