JAVA Unit 9 Arraylists
Retrieving value. Array or array list? String s = list.get(0);
Arraylist
Collections.reverse()
Reverse order of arraylist
Collections.sort(list, Comparator.comparing(s -> s.getX()))
Sort an arraylist using a specific key
boxing
Taking a primitive data element and wrapping it up in a wrapper class Ex. Double myDouble = new Double(6.0);
unboxing
Taking the primitive out of the wrapper Ex. double myPrimitive = myDouble.doubleValue();
Wrapper.typeValue()
Template for getting the primitive value in a wrapper.
Wrapper.parseType()
Template for parsing a value into a wrapper
<Class>
When constructing an ArrayList, you must specify thetype of elements it will contain between < and >. (also called type parameter)
list
a collection storing an ordered sequence of elements
add(value)
appends value at end of list
add(index, value)
inserts given value just before the given index, shifting subsequent values to the right
size
number of element that have been added
Wrapper
object whose sole purpose is to hold a primitive value
clear()
removes all elements of the list
remove(index)
removes/returns value at given index, shifting subsequent values to the left
set(index, value)
replaces value at given index with given value
toString()
returns a string representation of the list such as "[3, 42, -7, 15]"
indexOf(value)
returns first index where given value is found in list (-1 if not found)
toArray() list.toArray();
returns the elements in this list as an array
size()
returns the number of elements in list
get(index)
returns the value at given index
equals(list)
returns true if given other list contains the same elements
contains(value)
returns true if given value is found somewhere in this list