Quick Reference to Java Classes and Methods

The following classes have been used in class. Methods shown are either methods that we have covered or helpful methods from that class. The verbiage describing the method behavior comes from the java API's (Application Program Interface) which can be found at java.sun.com/j2se/1.5.0/docs/api/.

System class

This class contains some system variables and some methods which are used for input and output. (NOTE: The print methods are technically NOT part of the system class, but rather are part of the out object's class. For comprehension, I am including them here, but with the name of the object, out.

**Variables**
`static PrintStream`	`err` The "standard" output stream. (monitor)
`static InputStream`	`in` The "standard" input stream. (keyboard)
`static PrintStream`	`out` The standard output stream. (monitor)

**Methods:** Note: these are technically `PrintStream` methods (using the `out` object)
`void`	`out.print(String str)` Prints a string.
`void`	`out.printf(String str, Object...args)` A convenience method to write a formatted string to this output stream using the specified format string and arguments.
`void`	`out.println(String str)` Print a String and then terminate the line.
`void`	`out.println()` Terminate the current line by writing the line separator string.

Scanner Class

**methods**
	`Scanner(InputStream source)` Constructs a new Scanner that produces values scanned from the specified input stream. (We have always used this with `System.in` as our source)
`String`	`next()` Finds and returns the next complete token from this scanner.
`String`	`nextLine()` Advances this scanner past the current line and returns the input that was skipped.
`int`	`nextInt()` Scans the next token of the input as an int.
`double`	`nextDouble()` Scans the next token of the input as a double.
`Scanner`	`useDelimiter(String str)` Sets this scanner's delimiting pattern to a pattern constructed from the specified String.
`boolean`	`hasNext()` Returns `true` if this scanner has another token in its input.
`boolean`	`hasNextInt()` Returns `true` if the next token in this scanner's input can be interpreted as an int value in the default radix (base 10) using the `nextInt()` method.
`boolean`	`hasNextDouble()` Returns `true` if the next token in this scanner's input can be interpreted as a double value using the `nextDouble()` method.
`boolean`	`hasNextLine()` Returns `true` if there is another line in the input of this scanner.
NOTE: There are corresponding `next` and `hasNext` methods for all of the primitive types except for char.

Math Class

**variable**
`static double`	`Math.PI` - The `double` value that is closer than any other to pi, the ratio of the circumference of a circle to its diameter.

Integer Class

**variable**
`static integer`	`MAX_VALUE` - A constant holding the maximum value an int can have, 231-1.
`static integer`	`MIN_VALUE` - A constant holding the minimum value an int can have, -231.

String Class

**methods**
`int`	`length()` Returns the length of this string.
`char`	`charAt()` Returns the char value at the specified index.
`int`	`compareTo(String other)` Compares this String to the other String lexicographically. If the two are equal, the result is 0, if the calling String (this) is greater than the other String, the result is a positive integer. If the calling String (this) is less than the other String, the result is a negative integer.
`boolean`	`equals(String other)` Compares this string to the other String.
`boolean`	`equalsIgnoreCase(String other)` Compares this String to the other String, ignoring case considerations.