Standard Classes

1. Standard Classes

2. Classes we will discuss • Object • String • Wrapper Classes • Double • Integer • Math

3. Object • Superclass to all other classes • Methods • toString() • equals() • Unless overridden, returns true if this object and other object are same object, false otherwise. By “same” here, we mean same memory location • What if we want two objects to be considered equal if their contents are the same? Let’s override! POLYMORPHISM – WOOT WOOT • Note: • default .equals() is same as == • <, >, etc are not overridden in java. Must use .equals() and/or .compareTo() (Comparable interface, we’ll discuss more soon) • BankAccount.java • OrderedPair.java • Classes to write: BankAccount.java, OrderedPair.java, Client.java

4. String • A sequence of characters • Immutable objects – there are no methods to change them after they’ve been constructed • you can however create a new String which is a mutated version of an existing String • You can also reassign a String variable • String word = “abracadabra”; word = “supercalifragilisticexpealidocious”;

5. String methods and operators • Constructors • String name = “Mike”; • String name = new String(“Mike”); • Concatenation • String + String • String + primitive type • compareTo() • Compared lexicographically (think dictionary, or how files are sorted alphabetically) • Return value • int length() • String substring(intstartIndex) • String substring(intstartIndex, intendIndex) • intindexOf(String str) • intindexOf(char ch) • char charAt(int index) • boolean equals(Object o) • Look at == • booleanequalsIgnoreCase(String s) • String[] split(String delim) • String toUpperCase() • String toLowerCase()

6. Wrapper Classes • Takes existing object or primitive type and “wraps” or “boxes” it in an object • Provides new set of methods • Autoboxing – automatic conversion between primitive and corresponding reference type • Allows: • Construction of an object from a single value (wrapping/boxing) • Retrieval of primitive value (unwrapping/unboxing)

7. Wrapper Classes Integer Double Double(double value) double doubleValue() intcompareTo(Object o) boolean equals(Object o) String toString() • Integer(int value) – boxing • intintValue() – unboxing • intcompareTo(Object o) • boolean equals(Object o) • Overrides Object’s equals method • Throws ClassCastException if o is not an Integer • String toString() • Returns String representation of the Integer

8. Math • static int abs(int x) • static double abs(double x) • static double pow(double base, double exp) • static double sqrt(double x) • static double random() • static double floor(double x) • static double ceil(double x) • static long round(double x)

9. Note • There are MANY other methods in the classes we discuss that may be of use to you. Feel free to explore these in the Java API!!!!