Java Syntax Part I

1
Java Syntax Part I

• Comments
• Identifiers
• Primitive Data Types
• Assignment

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Java Syntax - Comments

• Type 1
• begins with /
• continues till the next /
• Type 2
• begins with //
• continues till the end of the line
• Type 3
• begins with /, and continues till the next /

3
Java Syntax -- comments (style)

• Good programming practice
• Put helpful comments
• at the beginning of a big block
• on the same line of certain statements
• Good internal documentation is very important

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Java Syntax -- comments (example)

• //--------------------------------------------
  -------------------------------
• // withdraw withdraw money from
  banking_account
• // Input amount the
  amount of money to withdraw
• //--------------------------------------------
  --------------------------------
• void withdraw(float amount)
• //----------- if not enough money in
  the account ----
• 
  
• //----------- else, we have enough
  money in the account ----
• ...

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Java Syntax -- Identifiers

• Names of declared entities
• variables, constans, labels
• Must start with a letter A..Za..z
• including _ (underscore) or (dollar sign)
• Followed by letters or digits
• Java language keywords can not be used as
  identifiers.

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Java Syntax -- Identifiers (example)

• accountNumber
• length1
• length_2

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Java Syntax -- Primitive Data Types

• boolean takes only 2 values true or false
• Example boolean done false
• char contains a character
• Example char ch
• byte, short, int and long Integral Types
• Example int num 3
• float, double Floating-Point Types
• Example float temperature 37.6

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Java Syntax -- Assignment

• Example using integers
• int i 2 // create an integer
  variable
• i 5 // change i to 5
• int j 6 // create an integer
  variable j
• i j3 // multifply the value of
  j by 3
• // now i 18
• i i 4 // NOT AN EQUATION!
• // i was 18, i422
  new i22.
• Calculate the value on the RIGHT HAND SIDE
• Assign the result to the variable on the LEFT
  HAND SIDE

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Java Syntax -- Assignment (Abbreviations)

• Examples
• j j 1 // as before
• j 1 // same as j j 1
• j 5 // same as j j 5
• j // same as j j 1