BasicCsTerms.md

Basic CS terms

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• Class: a blueprint for how a data structure should function.

• Constructor: instructs the class to set up the initial state of an object.

• Object: instance of a class that stores the state of a class.

• Method: set of instructions that can be called on an object.

• Parameter: values that can be specified when creating an object or calling a method.

• Return value: specifies the data type that a method will return after it runs.

• Inheritance: allows one class to use functionality defined in another class.

Data structures

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• ArrayList: stores a list of data of a specified type.

//Java
ArrayList<Integer> grades = new ArrayList<Integer>();
//To add values to an array, you can use the add() function;
grades.add(10);

• HashMap: a hashmap is like a dictionary containing sets of keys and a value for each key.

//Java
HashMap<String, Integer> friends = new HashMap<String, Integer>();
//To add values to a hashmap, you can use the put() function;
friends.put("Boo", 2);

Variable types

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• char: A single character. Should be initiated using single quotes. char is a primitive type.

char letter = 'a';

• string: Object containing multiple characters. Should be initiated with double quotes. String is not a primitive type, it's a reference type.

String text = "Hello world";

If trying to access a character in a string, the following triggers an error:

String dnaStrand;
int item = 0;
dnaStrand.charAt(item).toString();
//error: char cannot be dereferenced

As char is a primitive and not an object, it cannot be dereferenced. To access a character in a string, it should be done that way:

String dnaStrand;
int item = 0;
Character.toString(dnaStrand.charAt(item));

The 8 variable types are:

• boolean
• char
• int
• float
• byte
• short
• long
• double