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0) Last time- numerical types, conversion, operators, expressions

1) Administrative
- hw back
- codelab ch3 due next week
- hw: read 4.4 and 4.7, next person presents

2) Split in groups and go over 3.4-3.7

3) Highlights of material

	A) String: a class name (class names are capitalized by convention)
		* strings are sequences of characters
		* there are string literals, but no primitive type for strings
			- class is like a wrapper for a literal, with helpful methods
		* constructed like any object: String s = new String("Frodo");
			- there's a shortcut form: String s = "Frodo"; (only strings)
		* when you "add" strings, it's really concatenation
			- s + " Baggins" -> "Frodo Baggins"
		* wrapper classes - parallel wrappers for primitive types
			- Integer, Long, Double, Float (all very similar)
			- can create an object to wrap: Integer i = new Integer(5);
			- can just use static methods: int x= Integer.parseInt("26");

	B) String/number conversion
		* when's the only time it happens automatically?
			- concatenation: "test" + 1 -> "test1"
			- why is "test" + 1 + 2 -> "test12"? how do you get "test3"?
		* explicit number->string:  String s = Integer.toString(5); -> "5"
			- how could you force it w/o the call?    s = "" + 5;
		* explicit string->number: int i = Integer.parseInt("5"); -> 5
			- what if you send the wrong kind of parameter? runtime error
		* use JOptionPane to input a double with prompt "Dollars: "
			String input = JOptionPane.showInputDialog(null,"Dollars: ");
			double c = Double.parseDouble(input);
		* write it without the intermediate String variable, in one line
			double c= Double.parseDouble(JOptionPane.showInputDialog(..);
		* if there are 1.21 Euros/dollar, output "Euros: " and the amount
			JOptionPane.showMessageDialog(null, "Euros: "+1.21*c);

	C) Number formatting: library class DecimalFormat
		* above: 1.98*1.21 -> 2.3958, will print with all four places
		* write the code to print with only two
		   DecimalFormat df = new DecimalFormat("0.00");
		   JOptionPane.showMessageDialog(null,"Euros: "+df.format(1.21*c));
		* making an object, passing constructor a parameter, calling method
		
	D) Standard output: what you've seen already
		* anatomy of the call "System.out.print();"
			- class name (capitalized)
			- static data member of type PrintStream (prints to black)
			- method call on that object
		* difference b/w print() and println()?
		* how can you print "They say "Hello"" on the screen?
			System.out.print("They say \"Hello\"");
		* escape characters: \n, \t, \", \', \\

	E) Standard input: complicated, but better to look at than JOptionPanes
		* requires classes in the package "java.io", so import?  java.io.*;
		* what type of object reads a line?  BufferedReader
			BufferedReader buf = new BufferedReader(...);
		* what does it need as a parameter? object of InputStreamReader
			insert: (new InputStreamReader(...))
		* and what does THAT need?  System.in (static InputStream object)
			insert: (System.in)
		* it's a big mess, so get the idea and then just copy and paste it
		* now how do we read a line?   String s = buf.readLine();
			- no prompt, as in the window, so probably print one first
		* what could go wrong with this call?
			- IOException: put "throws IOException" in method header

	F) Math class: library class with helpful functions, all static
		* call with just the class name, w/o making a Math object
		* look at methods on pg 114
		* write code to calculate x = quadratic equation, given a, b, c
			double x = (-b + Math.sqrt(Math.pow(b,2) - 4*a*c)) / 2 / a;
		* write code to generate a random int r between 0 and 9
			int r = Math.floor(Math.random() * 10);

4) Exercise: write a main class with just the main method
	- prompt for user's height in inches
	- convert it to centimeters (2.54 cm/in) and round off (don't truncate)
	- print out a message with the converted value

	* type this on the overhead and run it, edit if necessary
	* go over commenting and blocking of the code

5) Summary
- string/number conversions
- number formatting
- standard input and output
- using Math class

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