Primitive Types

MultiMiniJ has three primitive types: boolean, int, and string.

Predefined Methods

Primitive types support the following predefined methods.

boolean

• string toString(): returns a string representation of this boolean value.

  {
    boolean b = true;
    string s = b.toString(); // assigns "true" into s.
  }
  

int

• string toString(): returns a string representation of this integer value.

  {
    int i = 23;
    string s = i.toString(); // assigns "23" into s.
  }
  

string

• string concat(string s): returns a new string value which represents the concatenation of this string with s.

  {
    string s1 = "Hello";
    string s2 = s1.concat(" world!"); // assigns "Hello world!" into s2.
  }
  

• string get(int index): returns a string of one character containing representing the index'th character of this string. The first character of a string has index 0.

  {
    string s1 = "Hello world!";
    string s2 = s1.get(6); // assigns "w" into s2.
  }
  

• int length(): returns the length of this string.

  {
    string s1 = "Hello world!";
    int len = s1.length(); // assigns 12 in len
  }
  

• boolean isInt(): returns true if this string is a number.

  {
    boolean b1 = "-12".isInt(); // assigns 'true' in b1
    boolean b2 = "12".isInt(); // assigns 'true' in b2
    boolean b3 = "-1".isInt(); // assigns 'true' in b3
    boolean b4 = "NotANumber".isInt(); // assigns 'false' in b4
  }
  

• int toInt(): converts this string to an integer. Aborts if something fails. Should be used along with isInt() to ensure that the result is valid and that the program executes normally.

  {
    int i1 = "-12".toInt(); // assigns -12 in i1
    int i2 = "12".toInt(); // assigns 12 in i2
    int i3 = "-1".toInt(); // assigns -1 in i3
    int i4 = "NotANumber".toInt(); // software abort
  }