# CSE143 Cheat Sheet

Below is an example of a method that could be added to the LinkedIntList class to compute the sum of the list:

public int sum() {

int sum = 0;

ListNode current = front;

while (current != null) {

sum += current.data;

current = current.next;

}

return sum;

}

### Math Methods (3.2)          mathematical operations

 Math.abs(value) absolute value Math.min(v1, v2) smaller of two values Math.max(v1, v2) larger of two values Math.round(value) nearest whole number Math.pow(b, e) b to the e power

### Two-dimensional Arrays (7.5)

construct a rectangular array with 4 rows and 6 columns:

int[][] data = new int;

construct a jagged array with different numbers of columns in each row (3 rows that have 2, 3, and 5 columns):

int[][] data = new int[];

data = new int;

data = new int;

data = new int;

Example values:

 data entire array data row 2 data value in row 2 and column 3 data.length number of rows data.length number of columns in row 2

### Iterator<E> Methods (11.1)                                     (An object that lets you examine the contents of any collection)

 hasNext() returns true if there are more elements to be read from collection next() reads and returns the next element from the collection remove() removes the last element returned by next from the collection

### List<E> Methods (10.1)                                                                                          (An ordered sequence of values)

 add(value) appends value at end of list add(index, value) inserts given value at given index, shifting subsequent values right clear() removes all elements of the list indexOf(value) returns first index where given value is found in list (-1 if not found) get(index) returns the value at given index remove(index) removes/returns value at given index, shifting subsequent values left set(index, value) replaces value at given index with given value size() returns the number of elements in list isEmpty() returns true if the list’s size is 0 addAll(collection) adds all elements from the given collection to the end of the list contains(value) returns true if the given value is found somewhere in this list remove(value) finds and removes the given value from this list removeAll(list) removes any elements found in the given collection from this list iterator() returns an object used to examine the contents of the list

### Set<E> Methods (11.2)                                                                                  (A fast-searchable set of unique values)

 add(value) adds the given value to the set contains(value) returns true if the given value is found in the set remove(value) removes the given value from the set clear() removes all elements of the set size() returns the number of elements in the set isEmpty() returns true if the set's size is 0 addAll(collection) adds all elements from the given collection to the set containsAll(collection) returns true if set contains every element from given collection removeAll(collection) removes any elements found in the given collection from this set retainAll(collection) removes any elements not found in the given collection from this set iterator() returns an object used to examine the contents of the set

### Map<K, V> Methods (11.3)                                                  (A fast mapping between a set of keys and a set of values)

 put(key, value) adds a mapping from the given key to the given value get(key) returns the value mapped to the given key (null if none) containsKey(key) returns true if the map contains a mapping for the given key remove(key) removes any existing mapping for the given key clear() removes all key/value pairs from the map size() returns the number of key/value pairs in the map isEmpty() returns true if the map's size is 0 keySet() returns a Set of all keys in the map values() returns a Collection of all values in the map putAll(map) adds all key/value pairs from the given map to this map

### Point Methods (8.1)                                                                              (an object for storing integer x/y coordinates)

 Point(x, y) constructs a new point with given x/y coordinates Point() constructs a new point with coordinates (0, 0) getX() returns the x-coordinate of this point getY() returns the y-coordinate of this point equals(other) returns true if this Point stores the same x/y values as the other translate(dx, dy) translates the coordinates by the given amount

### String Methods (3.3)                                                                         (An object for storing a sequence of characters)

 length() returns the number of characters in the string charAt(index) returns  thecharacter at a specific index compareTo(other) returns how this string compares to the other equals(other) returns true if this string equals the other toUpperCase() returns a new string with all uppercase letters toLowerCase() returns a new string with all lowercase letters startsWith(other) returns true if this string starts with the given text substring(start, stop) returns a new string composed of character from start index (inclusive) to stop index (exclusive)

### Collections Implementations

 List ArrayList and LinkedList Set HashSet and TreeSet (values ordered) Map HashMap and TreeMap (keys ordered)