See the JavaDocs for more detail.

abs() - Returns the absolute value of the argument. Overloaded for ints, longs, floats and doubles.

ceil(double) - Returns the smallest (closest to negative infinity) double value that is not less than the argument and is equal to a mathematical integer.

floor(double) - Returns the largest (closest to positive infinity) double value that is not greater than the argument and is equal to a mathematical integer.

max(value1,value2) - Returns the greater of two values.

min(value1,value2) - Returns the smaller of two values.

random() - Returns a random number between 0.0 and 1.0.

round(double) - Returns the closest long to the argument.

sin(double) - Returns the trigonometric sine of an angle. The angle is in radians.

cos(double) - Returns the trigonometric cosine of an angle. The angle is in radians.

tan(double) - Returns the trigonometric tangent of an angle. The angle is in radians.

sqrt(double) - Returns the square root of a double value.

String objects cannot be changed. They are assigned a sequence of characters when they are constructed. Look at the following code:

String message = "Good";
message= message + " morning";

When the first line executes, a string object containing "Good" is assigned to message. A new String object is constructed, unless the literal "Good" was used somewhere else, in which case the existing String is re-used. A consequence of this is the behaviour of the == operator which was describe under Language Fundamentals above, here is that information again:

[Note that if you construct two Strings with the same String literal, without using the new keyword, e.g.

String a = "Hello"
String b = "Hello"

, then Java creates only one String object, so a==b evaluates as true.]

On the second line, " morning" is appended. But the String object containing "Good" cannot be changed, so a new String, containing "Good morning" is created and assigned to message.

There are two fundamental types of variables in Java: primitives and objects. Sometimes a method or a constructor takes objects, but what what you have is a primitive. To cope with this situation, Java has a set of 'wrapper' classes which exist to hold the value of a primitive. For example, you might want to use a float as a key in a Map e.g. keying some business objects representing a loan by their respective interest rates. Using the Float class will allow you to do this. You would create a Float object for each value, and place that object into the Map.

The names are entirely obvious, except for the two that have been highlighted. Take a look at these classes in the JavaDocs. The pattern tends to be pretty similar: For a primitive type x, there is one constructor taking x and another that takes a String, which is parsed to get the value. There is a static parseX() method, which parses a string and returns the primitive type x. An xValue() method returns the underlying primitive value held by wrapped object. The toString() method from Object is overridden appropriately.

toHexString() is a static method on Integer and Long which creates a hexadecimal string representation of the argument as an unsigned integer in base 16.

©1999, 2000, 2002 Dylan Walsh.
Permission is granted to copy, distribute and/or modify this document under the terms of the GNU Free Documentation License, Version 1.1 or any later version published by the Free Software Foundation; with the Invariant Sections being the disclaimer, no Front-Cover Texts, and no Back-Cover Texts. A copy of the license is included in the section entitled "GNU Free Documentation License".