From the Sun Certified Programmer for Java 2 Platform 1.4 exam objectives:
Section 8: Fundamental Classes in the java.lang Package
# Write code using the following methods of the java.lang.Math class: abs, ceil, floor, max, min, random, round, sin, cos, tan, sqrt. # Describe the significance of the immutability of String objects. # Describe the significance of wrapper classes, including making appropriate selections in the wrapper classes to suit specified behavior requirements, stating the result of executing a fragment of code that includes an instance of one of the wrapper classes, and writing code using the following methods of the wrapper classes (e.g., Integer, Double, etc.): # o doubleValue # o floatValue # o intValue # o longValue # o parseXxx # o getXxx # o toString # o toHexString
If you want a reason why class Byte has no charValue() method, consider that a byte can be negative while a char can not.