Basic Java Language: Difference between revisions

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You can't create two variables with the same identifier, all identifiers must be unique. You also can't use an identifier that is a Java keyword. Here is a list of all the [http://en.wikipedia.org/wiki/Java_keywords Java Keywords]. [[Flashcards for Java keywords]] provides some assistance in memorizing the concepts behind specific keywords.

=Using the Displayer with Variables=

This section is about printing to the console using <code>System.out.println();</code>.

For Strings, it is extremely simple:

<code>System.out.println(STRING IDENTIFIER HERE);</code>

But for other variables, you have to do it like this:

<code>System.out.println(VARIABLE IDENT + "")</code>

This is because that method's parameter requires a string, and to change a variable to a string you say +"". Note that this only works on primitive types. On objects you have to have a method toString(). (You will read more).

Example:

<code>System.out.println(54 + "")</code>

You can also do multiple variables on the same line:

<code>System.out.println(false + 54 + "")</code>

You can put it anywhere: <code>System.out.println(false + "" + 54)</code>

Note that this won't work for two number values:

<code>System.out.println(54 + 32)</code>. It would mistake it for the adding operator for values. For strings, the operator is different. So you would have to do: <code>System.out.println(54+""+32)</code>

=Comments=

Comments are notes that the developer can insert into their code. This allows the developer to keep track of their code and helps when developers are collaborating on a project. It is good to write a summary of the following code at the beginning of your methods, classes, etc. The Java compiler completely ignores comments, so you can say anything in them

@@ Line 165: / Line 165: @@
 You can't create two variables with the same identifier, all identifiers must be unique. You also can't use an identifier that is a Java keyword. Here is a list of all the [http://en.wikipedia.org/wiki/Java_keywords Java Keywords].  [[Flashcards for Java keywords]] provides some assistance in memorizing the concepts behind specific keywords.
+=Using the Displayer with Variables=
+This section is about printing to the console using <code>System.out.println();</code>.
+For Strings, it is extremely simple:
+<code>System.out.println(STRING IDENTIFIER HERE);</code>
+But for other variables, you have to do it like this:
+<code>System.out.println(VARIABLE IDENT + "")</code>
+This is because that method's parameter requires a string, and to change a variable to a string you say +"". Note that this only works on primitive types. On objects you have to have a method toString(). (You will read more).
+Example:
+<code>System.out.println(54 + "")</code>
+You can also do multiple variables on the same line:
+<code>System.out.println(false + 54 + "")</code>
+You can put it anywhere: <code>System.out.println(false + "" + 54)</code>
+Note that this won't work for two number values:
+<code>System.out.println(54 + 32)</code>. It would mistake it for the adding operator for values. For strings, the operator is different. So you would have to do: <code>System.out.println(54+""+32)</code>
 =Comments=
 Comments are notes that the developer can insert into their code. This allows the developer to keep track of their code and helps when developers are collaborating on a project. It is good to write a summary of the following code at the beginning of your methods, classes, etc. The Java compiler completely ignores comments, so you can say anything in them

Basic Java Language: Difference between revisions

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