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% Document Info
\author{Jianmin Feng (taotao)}
\pdfinfo{
  /Title (java-methods-and-encapsulations.pdf)
  /Creator (Cheatography)
  /Author (Jianmin Feng (taotao))
  /Subject (Java Methods and encapsulations Cheat Sheet)
}

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    {\parbox{\dimexpr\textwidth-2\fboxsep\relax}{\noindent
        \hspace*{-6pt}\includegraphics[width=5.8cm]{/web/www.cheatography.com/public/images/cheatography_logo.pdf}}
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\begin{tabulary}{11cm}{L}
    \vspace{-2pt}\large{\bf{\textcolor{DarkBackground}{\textrm{Java Methods and encapsulations Cheat Sheet}}}} \\
    \normalsize{by \textcolor{DarkBackground}{Jianmin Feng (taotao)} via \textcolor{DarkBackground}{\uline{cheatography.com/79308/cs/19357/}}}
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  \mymulticolumn{2}{p{5.377cm}}{\bf\textcolor{white}{Cheatographer}}  \\
  \vspace{-2pt}Jianmin Feng (taotao) \\
  \uline{cheatography.com/taotao} \\
  \end{tabulary}
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  \mymulticolumn{1}{p{5.377cm}}{\bf\textcolor{white}{Cheat Sheet}}  \\
   \vspace{-2pt}Not Yet Published.\\
   Updated 8th May, 2019.\\
   Page {\thepage} of \pageref{LastPage}.
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  Measure your website readability!\\
  www.readability-score.com
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% Row Count 2 (+ 2)
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% Row 0
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Required & void =return; or no return statement \tn 
% Row Count 2 (+ 2)
% Row 1
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void method()\{return;\} & void method()\{\} \tn 
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% Row 2
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String method()\{return "";\} & String method()\{return null;\} \tn 
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String{[}{]} method()\{return null;\} & Integer method()\{return null;\} \tn 
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void method()\{return null;\} & This not compiled \tn 
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% Row 1
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same & No & yes & Yes \tn 
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% Row 3
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diff & Yes & yes & No * \tn 
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% Row 4
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diff & diff & No & No \tn 
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% Row 1
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shared component among instances & util/helper which not require any obj state \tn 
% Row Count 3 (+ 2)
% Row 2
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% Row Count 4 (+ 1)
% Row 3
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by class name & by obj ref ( null obj can too) \tn 
% Row Count 6 (+ 2)
% Row 4
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Static variables & Counter, Constant \tn 
% Row Count 7 (+ 1)
% Row 5
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Static initializer- run once & static \{....\}//bad practice \tn 
% Row Count 9 (+ 2)
% Row 6
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% Row Count 10 (+ 1)
% Row 7
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% Row Count 11 (+ 1)
% Row 8
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static import \seqsplit{java.util.Arrays.*;} & syntax error \tn 
% Row Count 13 (+ 2)
% Row 9
\SetRowColor{white}
import static java.util.Arrays; & Can not static import class \tn 
% Row Count 15 (+ 2)
% Row 10
\SetRowColor{LightBackground}
Name conflicts: not compiled & Solution: regular import,ref by classname \tn 
% Row Count 17 (+ 2)
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\SetRowColor{LightBackground}
\mymulticolumn{2}{x{5.377cm}}{Object has its status, but shared the code, and static data}  \tn 
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\mymulticolumn{4}{x{5.377cm}}{\bf\textcolor{white}{Static vs instance}}  \tn
% Row 0
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{\bf{type}} & {\bf{calling}} & {\bf{legal}} & {\bf{how}} \tn 
% Row Count 2 (+ 2)
% Row 1
\SetRowColor{white}
static method & static & Yes & Class name \tn 
% Row Count 4 (+ 2)
% Row 2
\SetRowColor{LightBackground}
static method & \seqsplit{instance} & No & create obj \tn 
% Row Count 6 (+ 2)
% Row 3
\SetRowColor{white}
instancd method & static & Yes & class name,obj ref \tn 
% Row Count 8 (+ 2)
% Row 4
\SetRowColor{LightBackground}
instance method & \seqsplit{instance} & Yes & obj ref \tn 
% Row Count 10 (+ 2)
\hhline{>{\arrayrulecolor{DarkBackground}}----}
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\mymulticolumn{4}{x{5.377cm}}{Object has its status, but shared the code, and static data}  \tn 
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pass by value & change in callee not affect caller \tn 
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% Row 1
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pass by ref & change in callee do affect caller \tn 
% Row Count 4 (+ 2)
% Row 2
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% Row 0
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Method signature & name+parameter list \tn 
% Row Count 2 (+ 2)
% Row 1
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\seqsplit{Overloading:} & same name+different parameters \tn 
% Row Count 4 (+ 2)
% Row 2
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varargs & 2nd test can't compile, varargs and array = same parameter list \tn 
% Row Count 7 (+ 3)
% Row 3
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 & void test(int... a)\{\}; void test(int{[}{]} a)\{\} \tn 
% Row Count 9 (+ 2)
% Row 4
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 & test(new \{1,2,3\}) call either \tn 
% Row Count 11 (+ 2)
% Row 5
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 & test(1,2,3) call test(int... a) only \tn 
% Row Count 13 (+ 2)
% Row 6
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autoboxing & void fly(int a)\{\}; void fly(Integer a)\{\}; \tn 
% Row Count 15 (+ 2)
% Row 7
\SetRowColor{white}
 & fly(3) call fly(int a); if not exit, call fly(Integer a) \tn 
% Row Count 17 (+ 2)
% Row 8
\SetRowColor{LightBackground}
Ref type & void fly(Object o)\{\}; \tn 
% Row Count 18 (+ 1)
% Row 9
\SetRowColor{white}
 & fly(3):match fly(int) \textgreater{}fly(Integer) \textgreater{}fly(Object o) \tn 
% Row Count 20 (+ 2)
% Row 10
\SetRowColor{LightBackground}
Primitive & autocast(wider), explicitly cast(narrower) \tn 
% Row Count 22 (+ 2)
% Row 11
\SetRowColor{white}
\mymulticolumn{2}{x{5.377cm}}{overloading matching order} \tn 
% Row Count 23 (+ 1)
% Row 12
\SetRowColor{LightBackground}
\mymulticolumn{2}{x{5.377cm}}{exact match  -\textgreater{} unwrapping -\textgreater{} promotion -\textgreater{} wrapping -\textgreater{}varargs(exact match, promotion, wrapper)} \tn 
% Row Count 25 (+ 2)
% Row 13
\SetRowColor{white}
\mymulticolumn{2}{x{5.377cm}}{promotion is an independent check, it retains no influence over wrapping check} \tn 
% Row Count 27 (+ 2)
% Row 14
\SetRowColor{LightBackground}
\mymulticolumn{2}{x{5.377cm}}{void play(Long l)\{\}} \tn 
% Row Count 28 (+ 1)
% Row 15
\SetRowColor{white}
\mymulticolumn{2}{x{5.377cm}}{play(4); compile error, 2 step conversion, only 1 conversion allowed, play(4L) will work.} \tn 
% Row Count 30 (+ 2)
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% Row 0
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Same name as class & no return type &  \tn 
% Row Count 2 (+ 2)
% Row 1
\SetRowColor{white}
default no-argument constructor & auto generated if no constructor provided &  \tn 
% Row Count 5 (+ 3)
% Row 2
\SetRowColor{LightBackground}
{\bf{overloading of constructor}} & Constructor chain & by \seqsplit{this(...)} \tn 
% Row Count 8 (+ 3)
% Row 3
\SetRowColor{white}
{\bf{Calling Constructo}}r & This(...): not in static method & first line of method \tn 
% Row Count 11 (+ 3)
% Row 4
\SetRowColor{LightBackground}
 & new Constructor(...) & Create new object \tn 
% Row Count 14 (+ 3)
% Row 5
\SetRowColor{white}
{\bf{final field}} & must be initialized by the time of constructor completion &  \tn 
% Row Count 18 (+ 4)
% Row 6
\SetRowColor{LightBackground}
{\bf{super()}} & call automatically in any constructor implicitly &  \tn 
% Row Count 21 (+ 3)
% Row 7
\SetRowColor{white}
 & all class are subclass of Object &  \tn 
% Row Count 23 (+ 2)
% Row 8
\SetRowColor{LightBackground}
{\bf{order of initialization}} & super() is always call in every constructor implicitly; super(...) must be called explicitly &  \tn 
% Row Count 29 (+ 6)
% Row 9
\SetRowColor{white}
\mymulticolumn{3}{x{5.377cm}}{super() -\textgreater{}static declaration and static \{\} as its order -\textgreater{}instance declaration and \{\} as its order -\textgreater{}constructor} \tn 
% Row Count 32 (+ 3)
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\mymulticolumn{3}{x{5.377cm}}{\bf\textcolor{white}{Create constructors (cont)}}  \tn
% Row 10
\SetRowColor{LightBackground}
\mymulticolumn{3}{x{5.377cm}}{{\bf{example}}} \tn 
% Row Count 1 (+ 1)
% Row 11
\SetRowColor{white}
class Bunny\{ \} & public bunny()\{\} & wrong \tn 
% Row Count 3 (+ 2)
% Row 12
\SetRowColor{LightBackground}
 & public Bunny()\{\} & OK \tn 
% Row Count 4 (+ 1)
% Row 13
\SetRowColor{white}
 & public void bunny()\{\} & OK \tn 
% Row Count 6 (+ 2)
% Row 14
\SetRowColor{LightBackground}
 & public void Bunny()\{\} & wrong \tn 
% Row Count 8 (+ 2)
\hhline{>{\arrayrulecolor{DarkBackground}}---}
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\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}{Encapsulating data}}  \tn
% Row 0
\SetRowColor{LightBackground}
\mymulticolumn{2}{x{5.377cm}}{Encapsulation: binding fields with method; data hiding(hiding \seqsplit{properties+implementation} details): private fields+public setter and getter; purpose: data validation and integrity + flexibility code for upgrade and maintenance} \tn 
% Row Count 5 (+ 5)
% Row 1
\SetRowColor{white}
private attributes & public getter(), setter(), isA() \tn 
% Row Count 7 (+ 2)
% Row 2
\SetRowColor{LightBackground}
{\bf{Immutable class}} & Math, String \tn 
% Row Count 8 (+ 1)
% Row 3
\SetRowColor{white}
Class w/o public setter & no status change of object once created \tn 
% Row Count 10 (+ 2)
% Row 4
\SetRowColor{LightBackground}
safe to passing around and easy to maintain & bette performance by limiting the number of copies ( string pool) \tn 
% Row Count 14 (+ 4)
% Row 5
\SetRowColor{white}
{\bf{String and StringBuffer}} & Mutated by StringBuffer, return a String \tn 
% Row Count 16 (+ 2)
% Row 6
\SetRowColor{LightBackground}
\mymulticolumn{2}{x{5.377cm}}{{\bf{JavaNean}}} \tn 
% Row Count 17 (+ 1)
% Row 7
\SetRowColor{white}
a class with no-argument constructor & naming convention:instance variable, getA,setA,isA, \tn 
% Row Count 20 (+ 3)
% Row 8
\SetRowColor{LightBackground}
reusable & easy to code \tn 
% Row Count 21 (+ 1)
\hhline{>{\arrayrulecolor{DarkBackground}}--}
\end{tabularx}
\par\addvspace{1.3em}

\begin{tabularx}{5.377cm}{x{1.78503 cm} x{2.19696 cm} p{0.59501 cm} }
\SetRowColor{DarkBackground}
\mymulticolumn{3}{x{5.377cm}}{\bf\textcolor{white}{Lambdas expression}}  \tn
% Row 0
\SetRowColor{LightBackground}
\mymulticolumn{3}{x{5.377cm}}{{\bf{Why lambdas?}}} \tn 
% Row Count 1 (+ 1)
% Row 1
\SetRowColor{white}
less code & delayed implementation & \seqsplit{declarative} \tn 
% Row Count 4 (+ 3)
% Row 2
\SetRowColor{LightBackground}
{\bf{what's lambdas?}} & a declarative block of code &  \tn 
% Row Count 6 (+ 2)
% Row 3
\SetRowColor{white}
\mymulticolumn{3}{x{5.377cm}}{passed to the associated 1 method interface, as delayed dynamic implement the method} \tn 
% Row Count 8 (+ 2)
% Row 4
\SetRowColor{LightBackground}
\mymulticolumn{3}{x{5.377cm}}{{\bf{Syntax}}} \tn 
% Row Count 9 (+ 1)
% Row 5
\SetRowColor{white}
parameter & -\textgreater{} & body \tn 
% Row Count 10 (+ 1)
% Row 6
\SetRowColor{LightBackground}
()-\textgreater{}true & simplest format &  \tn 
% Row Count 11 (+ 1)
% Row 7
\SetRowColor{white}
a-\textgreater{}a.canHop() & type is optonal &  \tn 
% Row Count 12 (+ 1)
% Row 8
\SetRowColor{LightBackground}
(Animal a) -\textgreater{}\{return a.canHop();\} & can't miss ; or return if use\{\}; need () if has type &  \tn 
% Row Count 15 (+ 3)
% Row 9
\SetRowColor{white}
(a,b)-\textgreater{}a.canHop() & () required if \textgreater{}1args; if \textgreater{}1 statement, need \{\} &  \tn 
% Row Count 18 (+ 3)
% Row 10
\SetRowColor{LightBackground}
{\bf{Context}} & functional method to match the only method of an interface &  \tn 
% Row Count 22 (+ 4)
% Row 11
\SetRowColor{white}
 & replace the implementing class of the interface &  \tn 
% Row Count 25 (+ 3)
% Row 12
\SetRowColor{LightBackground}
 & parameter type will be get from the associated interface API &  \tn 
% Row Count 29 (+ 4)
% Row 13
\SetRowColor{white}
\mymulticolumn{3}{x{5.377cm}}{{\bf{Notes}}} \tn 
% Row Count 30 (+ 1)
\end{tabularx}
\par\addvspace{1.3em}

\vfill
\columnbreak
\begin{tabularx}{5.377cm}{x{1.78503 cm} x{2.19696 cm} p{0.59501 cm} }
\SetRowColor{DarkBackground}
\mymulticolumn{3}{x{5.377cm}}{\bf\textcolor{white}{Lambdas expression (cont)}}  \tn
% Row 14
\SetRowColor{LightBackground}
\mymulticolumn{3}{x{5.377cm}}{lambdas expr could access static/instance variable. method parameter and local variable also fine if not assigned a new value} \tn 
% Row Count 3 (+ 3)
% Row 15
\SetRowColor{white}
\mymulticolumn{3}{x{5.377cm}}{can not redeclare a variable same name as local variable} \tn 
% Row Count 5 (+ 2)
% Row 16
\SetRowColor{LightBackground}
(a,b)-\textgreater{}\{int a=0;return 5;\} & won't compile &  \tn 
% Row Count 7 (+ 2)
\hhline{>{\arrayrulecolor{DarkBackground}}---}
\end{tabularx}
\par\addvspace{1.3em}

\begin{tabularx}{5.377cm}{X}
\SetRowColor{DarkBackground}
\mymulticolumn{1}{x{5.377cm}}{\bf\textcolor{white}{Lambdas example - Predicate}}  \tn
\SetRowColor{LightBackground}
\mymulticolumn{1}{x{5.377cm}}{//Predicate interface \newline public interface Predicate\textless{}T\textgreater{}\{ \newline     boolean test(T t); \} \newline  \newline // \newline class Animal\{ \newline   private String canHop; \newline   public void setCanHop(boolean b) \newline   \{    canHop =b; \} \newline   public boolean canHop() \newline   \{    return canHop; \} \newline \} \newline public interface CheckTrait \newline  \{   boolean test(Animal a); \} \newline public class CehckIfHopper implements CheckTrait\{ \newline    public boolean test(Animal a) \newline   \{ return a.canHop();\}  \newline \} \newline  \newline //compare  \newline import \seqsplit{java.util.function.Predicate;} \newline public class TestLambdas \{    \newline    public static void main(String{[}{]} args)\{ \newline      Animal a1 = new Animal(); \newline      a1.setCanHop(true); \newline      print (a1,a-\textgreater{}a.canHop());  \newline      // print2 (new checkIfHopper()); \newline    \} \newline    void print(Animal a, Predicate\textless{}Animal\textgreater{} p) \{ \newline       if (p.test(a) \{\} \} \newline  \newline    void print2(Animal a, CheckTrait c) \{ \newline       if (c.test(a) \{\}  \newline \} \newline //for Predicate version, no interface and implementing class needed \newline // \{return a.canHop();\} will be delayed dynamic implementation of test method in Predicate interface.} \tn 
\hhline{>{\arrayrulecolor{DarkBackground}}-}
\SetRowColor{LightBackground}
\mymulticolumn{1}{x{5.377cm}}{Type must match in lambda expr, or just do put type}  \tn 
\hhline{>{\arrayrulecolor{DarkBackground}}-}
\end{tabularx}
\par\addvspace{1.3em}

\begin{tabularx}{5.377cm}{X}
\SetRowColor{DarkBackground}
\mymulticolumn{1}{x{5.377cm}}{\bf\textcolor{white}{Lambdas - ArrayList.removeIf()}}  \tn
\SetRowColor{LightBackground}
\mymulticolumn{1}{x{5.377cm}}{//Java 8 intergrated Predicate interface into ArrayList \newline default boolean removeIf(Predicate\textless{}? super E\textgreater{} filter) \newline  \newline arrayList.removeIf(s-\textgreater{}s.charAt(0)!='h');} \tn 
\hhline{>{\arrayrulecolor{DarkBackground}}-}
\SetRowColor{LightBackground}
\mymulticolumn{1}{x{5.377cm}}{ArrayList\textless{}? super E\textgreater{} : super class of E, upper bound: "This can be cast to E". \newline ArrayList\textless{}? extends E\textgreater{}: hold type= subclass of E,  lower bound: "E can be cast to this." \newline ArrayList\textless{} E\textgreater{}: holder type E}  \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}{What happens after new Constructor()}}  \tn
% Row 0
\SetRowColor{LightBackground}
\mymulticolumn{2}{x{5.377cm}}{1. allocate memory space on the heap} \tn 
% Row Count 1 (+ 1)
% Row 1
\SetRowColor{white}
\mymulticolumn{2}{x{5.377cm}}{2. create the object and instance variables are initialized with default value} \tn 
% Row Count 3 (+ 2)
% Row 2
\SetRowColor{LightBackground}
\mymulticolumn{2}{x{5.377cm}}{3. explicit initialize the instance variabls} \tn 
% Row Count 4 (+ 1)
% Row 3
\SetRowColor{white}
\mymulticolumn{2}{x{5.377cm}}{4. constructor code are executed} \tn 
% Row Count 5 (+ 1)
% Row 4
\SetRowColor{LightBackground}
\mymulticolumn{2}{x{5.377cm}}{Notes:static variable are initialized once for all objects to be created, so it is before step 2} \tn 
% Row Count 7 (+ 2)
% Row 5
\SetRowColor{white}
\mymulticolumn{2}{x{5.377cm}}{for no argument constructor, super() is called first for initialization} \tn 
% Row Count 9 (+ 2)
\hhline{>{\arrayrulecolor{DarkBackground}}--}
\end{tabularx}
\par\addvspace{1.3em}


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

\end{document}