\documentclass[10pt,a4paper]{article}

% Packages
\usepackage{fancyhdr}           % For header and footer
\usepackage{multicol}           % Allows multicols in tables
\usepackage{tabularx}           % Intelligent column widths
\usepackage{tabulary}           % Used in header and footer
\usepackage{hhline}             % Border under tables
\usepackage{graphicx}           % For images
\usepackage{xcolor}             % For hex colours
%\usepackage[utf8x]{inputenc}    % For unicode character support
\usepackage[T1]{fontenc}        % Without this we get weird character replacements
\usepackage{colortbl}           % For coloured tables
\usepackage{setspace}           % For line height
\usepackage{lastpage}           % Needed for total page number
\usepackage{seqsplit}           % Splits long words.
%\usepackage{opensans}          % Can't make this work so far. Shame. Would be lovely.
\usepackage[normalem]{ulem}     % For underlining links
% Most of the following are not required for the majority
% of cheat sheets but are needed for some symbol support.
\usepackage{amsmath}            % Symbols
\usepackage{MnSymbol}           % Symbols
\usepackage{wasysym}            % Symbols
%\usepackage[english,german,french,spanish,italian]{babel}              % Languages

% Document Info
\author{Jianmin Feng (taotao)}
\pdfinfo{
  /Title (java-class-design-oca.pdf)
  /Creator (Cheatography)
  /Author (Jianmin Feng (taotao))
  /Subject (Java Class Design (OCA) Cheat Sheet)
}

% Lengths and widths
\addtolength{\textwidth}{6cm}
\addtolength{\textheight}{-1cm}
\addtolength{\hoffset}{-3cm}
\addtolength{\voffset}{-2cm}
\setlength{\tabcolsep}{0.2cm} % Space between columns
\setlength{\headsep}{-12pt} % Reduce space between header and content
\setlength{\headheight}{85pt} % If less, LaTeX automatically increases it
\renewcommand{\footrulewidth}{0pt} % Remove footer line
\renewcommand{\headrulewidth}{0pt} % Remove header line
\renewcommand{\seqinsert}{\ifmmode\allowbreak\else\-\fi} % Hyphens in seqsplit
% This two commands together give roughly
% the right line height in the tables
\renewcommand{\arraystretch}{1.3}
\onehalfspacing

% Commands
\newcommand{\SetRowColor}[1]{\noalign{\gdef\RowColorName{#1}}\rowcolor{\RowColorName}} % Shortcut for row colour
\newcommand{\mymulticolumn}[3]{\multicolumn{#1}{>{\columncolor{\RowColorName}}#2}{#3}} % For coloured multi-cols
\newcolumntype{x}[1]{>{\raggedright}p{#1}} % New column types for ragged-right paragraph columns
\newcommand{\tn}{\tabularnewline} % Required as custom column type in use

% Font and Colours
\definecolor{HeadBackground}{HTML}{333333}
\definecolor{FootBackground}{HTML}{666666}
\definecolor{TextColor}{HTML}{333333}
\definecolor{DarkBackground}{HTML}{1B752A}
\definecolor{LightBackground}{HTML}{F7FAF8}
\renewcommand{\familydefault}{\sfdefault}
\color{TextColor}

% Header and Footer
\pagestyle{fancy}
\fancyhead{} % Set header to blank
\fancyfoot{} % Set footer to blank
\fancyhead[L]{
\noindent
\begin{multicols}{3}
\begin{tabulary}{5.8cm}{C}
    \SetRowColor{DarkBackground}
    \vspace{-7pt}
    {\parbox{\dimexpr\textwidth-2\fboxsep\relax}{\noindent
        \hspace*{-6pt}\includegraphics[width=5.8cm]{/web/www.cheatography.com/public/images/cheatography_logo.pdf}}
    }
\end{tabulary}
\columnbreak
\begin{tabulary}{11cm}{L}
    \vspace{-2pt}\large{\bf{\textcolor{DarkBackground}{\textrm{Java Class Design (OCA) Cheat Sheet}}}} \\
    \normalsize{by \textcolor{DarkBackground}{Jianmin Feng (taotao)} via \textcolor{DarkBackground}{\uline{cheatography.com/79308/cs/19394/}}}
\end{tabulary}
\end{multicols}}

\fancyfoot[L]{ \footnotesize
\noindent
\begin{multicols}{3}
\begin{tabulary}{5.8cm}{LL}
  \SetRowColor{FootBackground}
  \mymulticolumn{2}{p{5.377cm}}{\bf\textcolor{white}{Cheatographer}}  \\
  \vspace{-2pt}Jianmin Feng (taotao) \\
  \uline{cheatography.com/taotao} \\
  \end{tabulary}
\vfill
\columnbreak
\begin{tabulary}{5.8cm}{L}
  \SetRowColor{FootBackground}
  \mymulticolumn{1}{p{5.377cm}}{\bf\textcolor{white}{Cheat Sheet}}  \\
   \vspace{-2pt}Not Yet Published.\\
   Updated 5th May, 2019.\\
   Page {\thepage} of \pageref{LastPage}.
\end{tabulary}
\vfill
\columnbreak
\begin{tabulary}{5.8cm}{L}
  \SetRowColor{FootBackground}
  \mymulticolumn{1}{p{5.377cm}}{\bf\textcolor{white}{Sponsor}}  \\
  \SetRowColor{white}
  \vspace{-5pt}
  %\includegraphics[width=48px,height=48px]{dave.jpeg}
  Measure your website readability!\\
  www.readability-score.com
\end{tabulary}
\end{multicols}}




\begin{document}
\raggedright
\raggedcolumns

% Set font size to small. Switch to any value
% from this page to resize cheat sheet text:
% www.emerson.emory.edu/services/latex/latex_169.html
\footnotesize % Small font.

\begin{multicols*}{3}

\begin{tabularx}{5.377cm}{p{0.4977 cm} p{0.4977 cm} }
\SetRowColor{DarkBackground}
\mymulticolumn{2}{x{5.377cm}}{\bf\textcolor{white}{Inheritance}}  \tn
% Row 0
\SetRowColor{LightBackground}
\mymulticolumn{2}{x{5.377cm}}{{\bf{Why inheritance?}}} \tn 
% Row Count 1 (+ 1)
% Row 1
\SetRowColor{white}
\mymulticolumn{2}{x{5.377cm}}{1. DRY(Don't Repeat Youself): No copy and paste, use has a (composition), is a ( inheritance)} \tn 
% Row Count 3 (+ 2)
% Row 2
\SetRowColor{LightBackground}
\mymulticolumn{2}{x{5.377cm}}{2. Extensible: easy to add/modify business logic and share the code)} \tn 
% Row Count 5 (+ 2)
% Row 3
\SetRowColor{white}
\mymulticolumn{2}{x{5.377cm}}{{\bf{Java inheritance}}} \tn 
% Row Count 6 (+ 1)
% Row 4
\SetRowColor{LightBackground}
\mymulticolumn{2}{x{5.377cm}}{Single inheritance, one parent only , all instance variables and methods inheritated} \tn 
% Row Count 8 (+ 2)
% Row 5
\SetRowColor{white}
\mymulticolumn{2}{x{5.377cm}}{one parent could have multiple child classes} \tn 
% Row Count 9 (+ 1)
% Row 6
\SetRowColor{LightBackground}
\mymulticolumn{2}{x{5.377cm}}{parent/super/generic \textless{}- child/sub/specifc} \tn 
% Row Count 10 (+ 1)
\hhline{>{\arrayrulecolor{DarkBackground}}--}
\end{tabularx}
\par\addvspace{1.3em}

\begin{tabularx}{5.377cm}{x{2.4885 cm} x{2.4885 cm} }
\SetRowColor{DarkBackground}
\mymulticolumn{2}{x{5.377cm}}{\bf\textcolor{white}{Chaining constructor}}  \tn
% Row 0
\SetRowColor{LightBackground}
\mymulticolumn{2}{x{5.377cm}}{{\bf{Chaining constructor}}} \tn 
% Row Count 1 (+ 1)
% Row 1
\SetRowColor{white}
\mymulticolumn{2}{x{5.377cm}}{child constructor call parent constructor} \tn 
% Row Count 2 (+ 1)
% Row 2
\SetRowColor{LightBackground}
\mymulticolumn{2}{x{5.377cm}}{reasons 1: private parent instance variable} \tn 
% Row Count 3 (+ 1)
% Row 3
\SetRowColor{white}
\mymulticolumn{2}{x{5.377cm}}{reasons 2:clean and neat:compare: loosen restrict, add using setter(how about set is not logically OK)} \tn 
% Row Count 6 (+ 3)
% Row 4
\SetRowColor{LightBackground}
\mymulticolumn{2}{x{5.377cm}}{super() is always called explicitly()or implicitly in the first line of child constructor. -\textgreater{} if a class will be extended, it must has no argument constructor, or do not have any constructor.} \tn 
% Row Count 10 (+ 4)
% Row 5
\SetRowColor{white}
\mymulticolumn{2}{x{5.377cm}}{super.xxx(dot operation on super) won't follow first line rule of constructor.} \tn 
% Row Count 12 (+ 2)
% Row 6
\SetRowColor{LightBackground}
\mymulticolumn{2}{x{5.377cm}}{{\bf{More on protected}}} \tn 
% Row Count 13 (+ 1)
% Row 7
\SetRowColor{white}
\mymulticolumn{2}{x{5.377cm}}{Package private + subclass} \tn 
% Row Count 14 (+ 1)
% Row 8
\SetRowColor{LightBackground}
parent/child + different packages, access protected state/behavior from parent & 1) direct call 2)obj ref of {\bf{the child}} itself 3) obj ref of parent or other sub class can NOT. \tn 
% Row Count 19 (+ 5)
\hhline{>{\arrayrulecolor{DarkBackground}}--}
\end{tabularx}
\par\addvspace{1.3em}

\begin{tabularx}{5.377cm}{x{2.4885 cm} x{2.4885 cm} }
\SetRowColor{DarkBackground}
\mymulticolumn{2}{x{5.377cm}}{\bf\textcolor{white}{Overriding}}  \tn
% Row 0
\SetRowColor{LightBackground}
\mymulticolumn{2}{x{5.377cm}}{in child change behavior of parent} \tn 
% Row Count 1 (+ 1)
% Row 1
\SetRowColor{white}
\mymulticolumn{2}{x{5.377cm}}{1. same signature as parent} \tn 
% Row Count 2 (+ 1)
% Row 2
\SetRowColor{LightBackground}
\mymulticolumn{2}{x{5.377cm}}{2. return type, same or subtype, primitive exact the same(no promoting and wrap)} \tn 
% Row Count 4 (+ 2)
% Row 3
\SetRowColor{white}
\mymulticolumn{2}{x{5.377cm}}{3. accessible: same or wider} \tn 
% Row Count 5 (+ 1)
% Row 4
\SetRowColor{LightBackground}
\mymulticolumn{2}{x{5.377cm}}{4. exception: same or fewer/subtype/runtime} \tn 
% Row Count 6 (+ 1)
% Row 5
\SetRowColor{white}
private/static methods are hidden, not overriden & polymorphism applies only instance method \tn 
% Row Count 9 (+ 3)
% Row 6
\SetRowColor{LightBackground}
\mymulticolumn{2}{x{5.377cm}}{super. ( dot notation) to access parent state or behavior} \tn 
% Row Count 11 (+ 2)
\hhline{>{\arrayrulecolor{DarkBackground}}--}
\SetRowColor{LightBackground}
\mymulticolumn{2}{x{5.377cm}}{never hiding static member ( variable/method) or instance variable, bad practice, confusing.}  \tn 
\hhline{>{\arrayrulecolor{DarkBackground}}--}
\end{tabularx}
\par\addvspace{1.3em}

\begin{tabularx}{5.377cm}{p{0.4977 cm} p{0.4977 cm} }
\SetRowColor{DarkBackground}
\mymulticolumn{2}{x{5.377cm}}{\bf\textcolor{white}{Covariant returns}}  \tn
% Row 0
\SetRowColor{LightBackground}
\mymulticolumn{2}{x{5.377cm}}{overriding method return a same or subtype of parent returned} \tn 
% Row Count 2 (+ 2)
% Row 1
\SetRowColor{white}
\mymulticolumn{2}{x{5.377cm}}{exact the same for primitive return} \tn 
% Row Count 3 (+ 1)
\hhline{>{\arrayrulecolor{DarkBackground}}--}
\end{tabularx}
\par\addvspace{1.3em}

\begin{tabularx}{5.377cm}{x{2.88666 cm} x{2.09034 cm} }
\SetRowColor{DarkBackground}
\mymulticolumn{2}{x{5.377cm}}{\bf\textcolor{white}{Three Faces of Final}}  \tn
% Row 0
\SetRowColor{LightBackground}
{\bf{final variable}} & Constant \tn 
% Row Count 1 (+ 1)
% Row 1
\SetRowColor{white}
enum constants implicitly static final & constant used in switch \tn 
% Row Count 3 (+ 2)
% Row 2
\SetRowColor{LightBackground}
{\bf{final method}} & no overriding \tn 
% Row Count 4 (+ 1)
% Row 3
\SetRowColor{white}
{\bf{final class}} & no extends, \seqsplit{java.lang.String} \tn 
% Row Count 6 (+ 2)
\hhline{>{\arrayrulecolor{DarkBackground}}--}
\SetRowColor{LightBackground}
\mymulticolumn{2}{x{5.377cm}}{Switch: literal,constant,enum, compiler time bind, variable or method return not, due to not known how many cases should be listed.}  \tn 
\hhline{>{\arrayrulecolor{DarkBackground}}--}
\end{tabularx}
\par\addvspace{1.3em}

\begin{tabularx}{5.377cm}{x{3.08574 cm} x{1.89126 cm} }
\SetRowColor{DarkBackground}
\mymulticolumn{2}{x{5.377cm}}{\bf\textcolor{white}{Class/Object invocation order}}  \tn
% Row 0
\SetRowColor{LightBackground}
1 static var=default & child-\textgreater{}base \tn 
% Row Count 1 (+ 1)
% Row 1
\SetRowColor{white}
2 static\{\}, explicit value assign to static var & base, in statement order \tn 
% Row Count 3 (+ 2)
% Row 2
\SetRowColor{LightBackground}
repeat 1,2 in child hierarchy order & -\textgreater{}child \tn 
% Row Count 5 (+ 2)
% Row 3
\SetRowColor{white}
4 instance var=default & child-\textgreater{}base \tn 
% Row Count 6 (+ 1)
% Row 4
\SetRowColor{LightBackground}
5 \{\},explicit value assign to instance var & base, in statement order \tn 
% Row Count 8 (+ 2)
% Row 5
\SetRowColor{white}
6 constructor & base \tn 
% Row Count 9 (+ 1)
% Row 6
\SetRowColor{LightBackground}
repeat 4,5,6 in child hierarchy order & -\textgreater{}child \tn 
% Row Count 11 (+ 2)
\hhline{>{\arrayrulecolor{DarkBackground}}--}
\SetRowColor{LightBackground}
\mymulticolumn{2}{x{5.377cm}}{static initialization 1-3 execute only once when first class is loaded.}  \tn 
\hhline{>{\arrayrulecolor{DarkBackground}}--}
\end{tabularx}
\par\addvspace{1.3em}

\begin{tabularx}{5.377cm}{x{2.18988 cm} x{2.78712 cm} }
\SetRowColor{DarkBackground}
\mymulticolumn{2}{x{5.377cm}}{\bf\textcolor{white}{Overloading}}  \tn
% Row 0
\SetRowColor{LightBackground}
same name+different parameters & Signature=name+param,unique in a class \tn 
% Row Count 2 (+ 2)
% Row 1
\SetRowColor{white}
\mymulticolumn{2}{x{5.377cm}}{Others(return type,modifiers, exceptions) not matter} \tn 
% Row Count 4 (+ 2)
% Row 2
\SetRowColor{LightBackground}
\mymulticolumn{2}{x{5.377cm}}{overloading matching order:} \tn 
% Row Count 5 (+ 1)
% Row 3
\SetRowColor{white}
\mymulticolumn{2}{x{5.377cm}}{exact match -\textgreater{}promoting-\textgreater{}wrapper =\textgreater{}varargs (exact match,promoting,wrapper)} \tn 
% Row Count 7 (+ 2)
\hhline{>{\arrayrulecolor{DarkBackground}}--}
\end{tabularx}
\par\addvspace{1.3em}

\begin{tabularx}{5.377cm}{p{0.4977 cm} p{0.4977 cm} }
\SetRowColor{DarkBackground}
\mymulticolumn{2}{x{5.377cm}}{\bf\textcolor{white}{Private methods redeclaration}}  \tn
% Row 0
\SetRowColor{LightBackground}
\mymulticolumn{2}{x{5.377cm}}{not inheritated} \tn 
% Row Count 1 (+ 1)
% Row 1
\SetRowColor{white}
\mymulticolumn{2}{x{5.377cm}}{can redecclare a method with same signature} \tn 
% Row Count 2 (+ 1)
\hhline{>{\arrayrulecolor{DarkBackground}}--}
\end{tabularx}
\par\addvspace{1.3em}

\begin{tabularx}{5.377cm}{p{0.4977 cm} p{0.4977 cm} }
\SetRowColor{DarkBackground}
\mymulticolumn{2}{x{5.377cm}}{\bf\textcolor{white}{hiding static method}}  \tn
% Row 0
\SetRowColor{LightBackground}
\mymulticolumn{2}{x{5.377cm}}{with static parent method, could not override} \tn 
% Row Count 1 (+ 1)
% Row 1
\SetRowColor{white}
\mymulticolumn{2}{x{5.377cm}}{hiding - no polymorphism} \tn 
% Row Count 2 (+ 1)
% Row 2
\SetRowColor{LightBackground}
\mymulticolumn{2}{x{5.377cm}}{4 overriding rules + static modifier} \tn 
% Row Count 3 (+ 1)
\hhline{>{\arrayrulecolor{DarkBackground}}--}
\SetRowColor{LightBackground}
\mymulticolumn{2}{x{5.377cm}}{Never hiding static methods in practice, confusing and bad habit}  \tn 
\hhline{>{\arrayrulecolor{DarkBackground}}--}
\end{tabularx}
\par\addvspace{1.3em}

\begin{tabularx}{5.377cm}{p{0.4977 cm} p{0.4977 cm} }
\SetRowColor{DarkBackground}
\mymulticolumn{2}{x{5.377cm}}{\bf\textcolor{white}{Inherite variables}}  \tn
% Row 0
\SetRowColor{LightBackground}
\mymulticolumn{2}{x{5.377cm}}{never overriding, always hiding if same name} \tn 
% Row Count 1 (+ 1)
% Row 1
\SetRowColor{white}
\mymulticolumn{2}{x{5.377cm}}{when hiding a variables, using super and this to access parent and child} \tn 
% Row Count 3 (+ 2)
% Row 2
\SetRowColor{LightBackground}
\mymulticolumn{2}{x{5.377cm}}{static and non static follow the same rule for hiding} \tn 
% Row Count 5 (+ 2)
% Row 3
\SetRowColor{white}
\mymulticolumn{2}{x{5.377cm}}{private variables inherited but could not access directly.} \tn 
% Row Count 7 (+ 2)
\hhline{>{\arrayrulecolor{DarkBackground}}--}
\SetRowColor{LightBackground}
\mymulticolumn{2}{x{5.377cm}}{never hiding variables in practice, confusing and hard to read code}  \tn 
\hhline{>{\arrayrulecolor{DarkBackground}}--}
\end{tabularx}
\par\addvspace{1.3em}

\begin{tabularx}{5.377cm}{p{0.4977 cm} p{0.4977 cm} }
\SetRowColor{DarkBackground}
\mymulticolumn{2}{x{5.377cm}}{\bf\textcolor{white}{Abstract classes}}  \tn
% Row 0
\SetRowColor{LightBackground}
\mymulticolumn{2}{x{5.377cm}}{{\bf{Why?}}} \tn 
% Row Count 1 (+ 1)
% Row 1
\SetRowColor{white}
\mymulticolumn{2}{x{5.377cm}}{generalization, inheritance, overriding and  polymorphism} \tn 
% Row Count 3 (+ 2)
% Row 2
\SetRowColor{LightBackground}
\mymulticolumn{2}{x{5.377cm}}{simply code, beauty, no DRY} \tn 
% Row Count 4 (+ 1)
% Row 3
\SetRowColor{white}
\mymulticolumn{2}{x{5.377cm}}{prevent improper instantiate of parent classes} \tn 
% Row Count 5 (+ 1)
% Row 4
\SetRowColor{LightBackground}
\mymulticolumn{2}{x{5.377cm}}{{\bf{Abstract class rules}}} \tn 
% Row Count 6 (+ 1)
% Row 5
\SetRowColor{white}
\mymulticolumn{2}{x{5.377cm}}{\textgreater{}=0 abstract methods} \tn 
% Row Count 7 (+ 1)
% Row 6
\SetRowColor{LightBackground}
\mymulticolumn{2}{x{5.377cm}}{can't initialized} \tn 
% Row Count 8 (+ 1)
% Row 7
\SetRowColor{white}
\mymulticolumn{2}{x{5.377cm}}{public /package private only, must be extends, so private or final is not allowed, protected is not logic/meaningful} \tn 
% Row Count 11 (+ 3)
% Row 8
\SetRowColor{LightBackground}
\mymulticolumn{2}{x{5.377cm}}{extends abstract class means overriden all abstracted methods or declared as abstract} \tn 
% Row Count 13 (+ 2)
% Row 9
\SetRowColor{white}
\mymulticolumn{2}{x{5.377cm}}{first concrete class must have implemented all abstract method directly or indirectly} \tn 
% Row Count 15 (+ 2)
% Row 10
\SetRowColor{LightBackground}
\mymulticolumn{2}{x{5.377cm}}{{\bf{Abstract methods}}} \tn 
% Row Count 16 (+ 1)
% Row 11
\SetRowColor{white}
\mymulticolumn{2}{x{5.377cm}}{in abstract class} \tn 
% Row Count 17 (+ 1)
% Row 12
\SetRowColor{LightBackground}
\mymulticolumn{2}{x{5.377cm}}{can not be private, final, static (must be overriden)} \tn 
% Row Count 19 (+ 2)
% Row 13
\SetRowColor{white}
\mymulticolumn{2}{x{5.377cm}}{no body, even \{\}} \tn 
% Row Count 20 (+ 1)
% Row 14
\SetRowColor{LightBackground}
\mymulticolumn{2}{x{5.377cm}}{overriding rules(4) must be followed: same signature, broader or same visibility, narrower or same return type, narrower or same exception throws/or runtime exception} \tn 
% Row Count 24 (+ 4)
\hhline{>{\arrayrulecolor{DarkBackground}}--}
\end{tabularx}
\par\addvspace{1.3em}

\begin{tabularx}{5.377cm}{x{2.4885 cm} x{2.4885 cm} }
\SetRowColor{DarkBackground}
\mymulticolumn{2}{x{5.377cm}}{\bf\textcolor{white}{Interface}}  \tn
% Row 0
\SetRowColor{LightBackground}
\mymulticolumn{2}{x{5.377cm}}{public abstract interface ....\{\}} \tn 
% Row Count 1 (+ 1)
% Row 1
\SetRowColor{white}
public static final MIN\_DEPTH=3 & init at the statement \tn 
% Row Count 3 (+ 2)
% Row 2
\SetRowColor{LightBackground}
interface extends interface1,interface2,... & multiple extends allowed here \tn 
% Row Count 6 (+ 3)
% Row 3
\SetRowColor{white}
class inpluments interface1,interface2,... & multiple implements \tn 
% Row Count 9 (+ 3)
% Row 4
\SetRowColor{LightBackground}
\mymulticolumn{2}{x{5.377cm}}{can redecclare a method with same signature} \tn 
% Row Count 10 (+ 1)
% Row 5
\SetRowColor{white}
\mymulticolumn{2}{x{5.377cm}}{{\bf{Rule for interface}}} \tn 
% Row Count 11 (+ 1)
% Row 6
\SetRowColor{LightBackground}
can not instantiated & may have no methods at all \tn 
% Row Count 13 (+ 2)
% Row 7
\SetRowColor{white}
public / default only & not private,final, protected for interface \tn 
% Row Count 16 (+ 3)
% Row 8
\SetRowColor{LightBackground}
all methods must be public & not private,final, protected for methods \tn 
% Row Count 18 (+ 2)
% Row 9
\SetRowColor{white}
abstract method by default & in java8, default, static methods with a body allowed \tn 
% Row Count 21 (+ 3)
% Row 10
\SetRowColor{LightBackground}
{\bf{default interface methods}} & java 8 \tn 
% Row Count 23 (+ 2)
% Row 11
\SetRowColor{white}
\mymulticolumn{2}{x{5.377cm}}{mainly for backward compatibility} \tn 
% Row Count 24 (+ 1)
% Row 12
\SetRowColor{LightBackground}
\mymulticolumn{2}{x{5.377cm}}{public default double calc()\{\}} \tn 
% Row Count 25 (+ 1)
% Row 13
\SetRowColor{white}
only in interface & can be redeclared as abstract or overriden with a different body \tn 
% Row Count 29 (+ 4)
% Row 14
\SetRowColor{LightBackground}
not static, final,or abstract ( overriden) & not private,protected \tn 
% Row Count 32 (+ 3)
\end{tabularx}
\par\addvspace{1.3em}

\vfill
\columnbreak
\begin{tabularx}{5.377cm}{x{2.4885 cm} x{2.4885 cm} }
\SetRowColor{DarkBackground}
\mymulticolumn{2}{x{5.377cm}}{\bf\textcolor{white}{Interface (cont)}}  \tn
% Row 15
\SetRowColor{LightBackground}
\mymulticolumn{2}{x{5.377cm}}{{\bf{Multiple inheritance problem}}} \tn 
% Row Count 1 (+ 1)
% Row 16
\SetRowColor{white}
\mymulticolumn{2}{x{5.377cm}}{default method in interface, if not overriden, will cause compiler error if default methods with same signuature existed} \tn 
% Row Count 4 (+ 3)
% Row 17
\SetRowColor{LightBackground}
\mymulticolumn{2}{x{5.377cm}}{for interfaces without default methods, there is no this issue} \tn 
% Row Count 6 (+ 2)
% Row 18
\SetRowColor{white}
\mymulticolumn{2}{x{5.377cm}}{if default method is overriden, also no ambiguity problem.} \tn 
% Row Count 8 (+ 2)
% Row 19
\SetRowColor{LightBackground}
{\bf{Static method}} & java 8 above \tn 
% Row Count 9 (+ 1)
% Row 20
\SetRowColor{white}
public or default only & with a body \tn 
% Row Count 11 (+ 2)
% Row 21
\SetRowColor{LightBackground}
call with interface name, not with object ref & this avoid ambiguity cause be multiple inheritance \tn 
% Row Count 14 (+ 3)
% Row 22
\SetRowColor{white}
\mymulticolumn{2}{x{5.377cm}}{static methods in interface could be declared as default in sub interface} \tn 
% Row Count 16 (+ 2)
% Row 23
\SetRowColor{LightBackground}
\mymulticolumn{2}{x{5.377cm}}{designed to offer utility functions} \tn 
% Row Count 17 (+ 1)
\hhline{>{\arrayrulecolor{DarkBackground}}--}
\SetRowColor{LightBackground}
\mymulticolumn{2}{x{5.377cm}}{protected method in interface does not makes sense as has nothing to be shared with the subclass. it is just an interface. \newline muliple inheritance of type: \newline https://docs.oracle.com/javase/tutorial/java/IandI/multipleinheritance.htm \newline https://www.baeldung.com/java-static-default-methods \newline https://www.geeksforgeeks.org/difference-between-abstract-class-and-interface-in-java/}  \tn 
\hhline{>{\arrayrulecolor{DarkBackground}}--}
\end{tabularx}
\par\addvspace{1.3em}

\begin{tabularx}{5.377cm}{x{2.4885 cm} x{2.4885 cm} }
\SetRowColor{DarkBackground}
\mymulticolumn{2}{x{5.377cm}}{\bf\textcolor{white}{Polymorphism}}  \tn
% Row 0
\SetRowColor{LightBackground}
heart of inheritance ( \seqsplit{overriding+polymorphism)} & separate of concern, flexible/extensible coding \tn 
% Row Count 3 (+ 3)
% Row 1
\SetRowColor{white}
\mymulticolumn{2}{x{5.377cm}}{properties of an object to take on many different forms,compiling time- ref by super class/interface ref, at run time multiple behavior,based on the object itself} \tn 
% Row Count 7 (+ 4)
% Row 2
\SetRowColor{LightBackground}
multiple references(on the stack) ( ref of type of super class, interface), static binding & multiple object (on the heap )behaviors, dynamic binding \tn 
% Row Count 12 (+ 5)
% Row 3
\SetRowColor{white}
{\bf{Virtual methods}} & dynamic method dispatching \tn 
% Row Count 14 (+ 2)
% Row 4
\SetRowColor{LightBackground}
overriden methods & non private,static,final \tn 
% Row Count 16 (+ 2)
% Row 5
\SetRowColor{white}
\mymulticolumn{2}{x{5.377cm}}{a method in  which the specific implementation is not determined until run time; at compiling time, parent ref is used, at run time, implementation based on the child obj referenced} \tn 
% Row Count 20 (+ 4)
% Row 6
\SetRowColor{LightBackground}
\mymulticolumn{2}{x{5.377cm}}{{\bf{Object casting}}} \tn 
% Row Count 21 (+ 1)
% Row 7
\SetRowColor{white}
\mymulticolumn{2}{x{5.377cm}}{implicit up casting ( child -\textgreater{}parent)} \tn 
% Row Count 22 (+ 1)
% Row 8
\SetRowColor{LightBackground}
\mymulticolumn{2}{x{5.377cm}}{explicity down casting( parent-\textgreater{}child)} \tn 
% Row Count 23 (+ 1)
% Row 9
\SetRowColor{white}
error for non-parent/child object casting & safe casting: \seqsplit{obj1.instanceOf(obj2)} \tn 
% Row Count 26 (+ 3)
% Row 10
\SetRowColor{LightBackground}
\mymulticolumn{2}{x{5.377cm}}{{\bf{Polymorphic parameters}}} \tn 
% Row Count 27 (+ 1)
% Row 11
\SetRowColor{white}
\mymulticolumn{2}{x{5.377cm}}{parameter is parent class or interface type} \tn 
% Row Count 28 (+ 1)
% Row 12
\SetRowColor{LightBackground}
passing the child obj or obj implemented the interface & auto up casting \tn 
% Row Count 31 (+ 3)
\hhline{>{\arrayrulecolor{DarkBackground}}--}
\SetRowColor{LightBackground}
\mymulticolumn{2}{x{5.377cm}}{a reference variable may only send messages that are available to its type.being available to an object != being declared inside an object}  \tn 
\hhline{>{\arrayrulecolor{DarkBackground}}--}
\end{tabularx}
\par\addvspace{1.3em}

\begin{tabularx}{5.377cm}{p{0.4977 cm} p{0.4977 cm} }
\SetRowColor{DarkBackground}
\mymulticolumn{2}{x{5.377cm}}{\bf\textcolor{white}{when Parent/Child not belong to same package}}  \tn
% Row 0
\SetRowColor{LightBackground}
\mymulticolumn{2}{x{5.377cm}}{{\bf{in extending class}}} \tn 
% Row Count 1 (+ 1)
% Row 1
\SetRowColor{white}
\mymulticolumn{2}{x{5.377cm}}{protected parent members could be access directly. if by references, only by the ref of extending class itself} \tn 
% Row Count 4 (+ 3)
% Row 2
\SetRowColor{LightBackground}
\mymulticolumn{2}{x{5.377cm}}{ref variables of other child class or event he parent class COULD NOT access parent members inside extending calss} \tn 
% Row Count 7 (+ 3)
% Row 3
\SetRowColor{white}
\mymulticolumn{2}{x{5.377cm}}{{\bf{constructor()}}} \tn 
% Row Count 8 (+ 1)
% Row 4
\SetRowColor{LightBackground}
\mymulticolumn{2}{x{5.377cm}}{if constructor missing access modifier ( package private), the child class could not instantiated.} \tn 
% Row Count 10 (+ 2)
% Row 5
\SetRowColor{white}
\mymulticolumn{2}{x{5.377cm}}{if class to be extends, constructor must be public or protected, if in different package.} \tn 
% Row Count 12 (+ 2)
\hhline{>{\arrayrulecolor{DarkBackground}}--}
\end{tabularx}
\par\addvspace{1.3em}

\begin{tabularx}{5.377cm}{p{0.4977 cm} p{0.4977 cm} }
\SetRowColor{DarkBackground}
\mymulticolumn{2}{x{5.377cm}}{\bf\textcolor{white}{Pass by value vs by reference}}  \tn
% Row 0
\SetRowColor{LightBackground}
\mymulticolumn{2}{x{5.377cm}}{Both are passing by copy} \tn 
% Row Count 1 (+ 1)
% Row 1
\SetRowColor{white}
\mymulticolumn{2}{x{5.377cm}}{the original content ( primitive value or object memory address) variables not affected} \tn 
% Row Count 3 (+ 2)
% Row 2
\SetRowColor{LightBackground}
\mymulticolumn{2}{x{5.377cm}}{if passing a copy of obj address, changes to the object on the heap will shared with all references.} \tn 
% Row Count 5 (+ 2)
% Row 3
\SetRowColor{white}
\mymulticolumn{2}{x{5.377cm}}{reassign the reference in callee will not affect the ref in caller} \tn 
% Row Count 7 (+ 2)
% Row 4
\SetRowColor{LightBackground}
\mymulticolumn{2}{x{5.377cm}}{variable on stack frame, obj on heap} \tn 
% Row Count 8 (+ 1)
\hhline{>{\arrayrulecolor{DarkBackground}}--}
\end{tabularx}
\par\addvspace{1.3em}


% That's all folks
\end{multicols*}

\end{document}