AP Computer Science A Java Quick Reference Implementations

This library contains implementations for the AP Computer Science A Java Quick Reference as specified by College Board. As of 2022, the standard is defined as follows:

Class Constructors and Methods	Explanation
String(String str)	Constructs a new String object that represents the same sequence of characters as str
int length()	Returns the number of characters in a String object
String substring(int from, int to)	Returns the substring beginning at index from and ending at index to - 1
String substring(int from)	Returns substring(from, length())
int indexOf(String str)	Returns the index of the first occurrence of str; returns -1 if not found
boolean equals(String other)	Returns true if this is equal to other; returns false otherwise
int compareTo(String other)	Returns a value <0 if this is less than other; returns zero if this is equal to other; returns a value >0 if this is greater than other
Integer(int value)	Constructs a new Integer object that represents the specified int value
Integer.MIN_VALUE	The minimum value represented by an int or Integer
Integer.MAX_VALUE	The maximum value represented by an int or Integer
int intValue()	Returns the value of this Integer as an int
Double(double value)	Constructs a new Double object that represents the specified double value
double doubleValue()	Returns the value of this Double as a double
static int abs(int x)	Returns the absolute value of an int value
static double abs(double x)	Returns the absolute value of an double value
static double pow(double base, double exponent)	Returns the value of the first parameter raised to the power of the second parameter
static double sqrt(double x)	Returns the positive square root of a double value
static double random()	Returns a double value greater than or equal to 0.0 and less than 1.0
int size()	Returns the number of elements in the list
boolean add(E obj)	Appends obj to end of list; returns true
void add(int index, E obj)	Inserts obj at position index (0 <= index <= size), moving elements at position index and higher to the right (adds 1 to their indices) and adds 1 to size
E get(int index)	Returns the element at position index in the list
E set(int index, E obj)	Replaces the element at position index with obj; returns the element formely at position index
E remove(int index)	Removes element from position index, moving elements at position index + 1 and higher to the left (subtracts 1 from their indices) and subtracts 1 from size; returns the element formely at position index

Implementation Details

As the Quick Reference already uses Java's standard library as its foundation, this library serves no practical purpose outside the teaching environment. Its creation is meant for educators and students to learn about the implementations of frequently discussed concepts in the Advanced Placement Computer Science A curriculum.

• ❌ IT IS NOT: a wrapper for Java's standard library.
• ❌ IT IS NOT: an efficient or highly-optimized library; use Java's standard library for all practical purposes.
• ❌ IT DOES NOT: contain all the methods for specified classes. (ONLY contains the methods listed in the Quick Reference; for example, this String class doesn't have char charAt(int index).)
• ❌ IT DOES NOT: follow enterprise documentation conventions; it is merely a teaching tool.
• ✔️IT DOES: allow learners to explore the inner-workings of common Java functions without cluttered boilerplate code.
• ✔️IT DOES: actually work! The implmentation behaves according to the Quick Reference and is fully tested with AP Free Response Questions and custom-defined objectives.
• ✔️IT DOES: balance time and space complexity with the difficulty of algorithms. (Maybe not the most efficient, but very easy to understand.)

Every method will be furnished with comments and documentation and the implementation will always be the most intuitive and simple to grasp, although the implementations are NOT reflective of Java's official implementations. The goal is to provide accurate and simple implementations for learners who may feel daunted when looking at Java's source code.

How To Use

Download the JAR library in the "Releases" section and add it as an external JAR reference to start using the library. Ways of importing the JAR may differ between IDEs, so please search up how to import a JAR library as your mileage may vary. Except for the ArrayList class, all other classes are defined in java.lang, which may cause confusion in naming. To prevent this ambiguity, the recommended way of defining all objects is as follows:

import ap.compscia.ArrayList; // only ArrayList can be imported

public class Example {
    
    public static void main(String[] args) {
        ArrayList<E> arrayList = new ArrayList<E>(); // refers to ap.compscia.ArrayList
        Integer someInt = 59; // this refers to java.lang.Integer
        ap.compscia.Integer someApInt = ap.compscia.Integer(59); // different from Java's built-in Integer wrapper class
        Double someDouble = 495.5; // this refers to java.lang.Double
        ap.compscia.Double someApDouble = ap.compscia.Double(495.5); // different from Java's built-in Double wrapper class
    }
}