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% Document Info
\author{Giang.nd2508}
\pdfinfo{
  /Title (java-intermediate-collection.pdf)
  /Creator (Cheatography)
  /Author (Giang.nd2508)
  /Subject (Java\_Intermediate: Collection Cheat Sheet)
}

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\noindent
\begin{multicols}{3}
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    \vspace{-7pt}
    {\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\_Intermediate: Collection Cheat Sheet}}}} \\
    \normalsize{by \textcolor{DarkBackground}{Giang.nd2508} via \textcolor{DarkBackground}{\uline{cheatography.com/134606/cs/30401/}}}
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\begin{multicols}{3}
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  \SetRowColor{FootBackground}
  \mymulticolumn{2}{p{5.377cm}}{\bf\textcolor{white}{Cheatographer}}  \\
  \vspace{-2pt}Giang.nd2508 \\
  \uline{cheatography.com/giang-nd2508} \\
  \end{tabulary}
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  \mymulticolumn{1}{p{5.377cm}}{\bf\textcolor{white}{Cheat Sheet}}  \\
   \vspace{-2pt}Published 8th January, 2022.\\
   Updated 16th February, 2022.\\
   Page {\thepage} of \pageref{LastPage}.
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  Measure your website readability!\\
  www.readability-score.com
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\begin{multicols*}{2}

\begin{tabularx}{8.4cm}{X}
\SetRowColor{DarkBackground}
\mymulticolumn{1}{x{8.4cm}}{\bf\textcolor{white}{Collection}}  \tn
\SetRowColor{white}
\mymulticolumn{1}{x{8.4cm}}{- is a "bag" = unordered lists \newline % Row Count 1 (+ 1)
- No direct implementation% Row Count 2 (+ 1)
} \tn 
\hhline{>{\arrayrulecolor{DarkBackground}}-}
\end{tabularx}
\par\addvspace{1.3em}

\begin{tabularx}{8.4cm}{X}
\SetRowColor{DarkBackground}
\mymulticolumn{1}{x{8.4cm}}{\bf\textcolor{white}{Collection Methods}}  \tn
\SetRowColor{LightBackground}
\mymulticolumn{1}{x{8.4cm}}{Collection\textless{}String\textgreater{} names = new ArrayList\textless{}\textgreater{}(); \newline  \newline - {\bf{Add one element}} \newline names.add("john"); \newline System.out.println(names); //{[}john{]} \newline  \newline - {\bf{Add multiple elements}} \newline names.addAll(List.of("james, harry")); \newline System.out.println(names); //{[}james, harry{]} \newline  \newline -{}-{}-{}-{}-{}-{}-{}-{}-{}-{}-{}-{}-{}-{}-{}-{}-{}-{}-{}-{}-{}-{}-{}-{}-{}-{}-{}-{}-{}-{}-{}-{}-{}-{}-{}-{}-{}-{}-{}-- \newline  \newline Collection\textless{}String\textgreater{} names = new ArrayList\textless{}\textgreater{}(List.of("john", "james", "harry")); \newline  \newline - {\bf{Remove one element}} \newline names.remove("john"); \newline System.out.println(names); //{[}james, harry{]} \newline  \newline - {\bf{Remove multiple elements}} \newline names.removeAll(List.of("james", "harry")); \newline System.out.println(names); //{[}john{]} \newline  \newline - {\bf{Remove based on a condition}} \newline names.removeIf(s -\textgreater{} s.startsWith("j")); \newline System.out.println(names); //{[}harry{]} \newline  \newline - {\bf{Remove all elements}} \newline names.clear(); \newline System.out.println(names); //{[}{]} \newline  \newline - {\bf{Remove the differences}} \newline Collection\textless{}String\textgreater{} names2 = new ArrayList\textless{}\textgreater{}(List.of("john", "james", "Steve")); \newline names.retainAll(names2); \newline System.out.println(names); //{[}john, james{]} \newline  \newline -{}-{}-{}-{}-{}-{}-{}-{}-{}-{}-{}-{}-{}-{}-{}-{}-{}-{}-{}-{}-{}-{}-{}-{}-{}-{}-{}-{}-{}-{}-{}-{}-{}-{}-{}-{}-{}-{}-{}-- \newline  \newline Collection\textless{}String\textgreater{} names = new ArrayList\textless{}\textgreater{}(List.of("john", "james", "harry")); \newline  \newline - {\bf{Print each element}} \newline names.forEach(System.out::println); //john james harry \newline  \newline - {\bf{Get size}} \newline System.out.println(names.size()); //3 \newline  \newline - {\bf{Check empty}} \newline System.out.println(names.isEmpty()); //false \newline  \newline - {\bf{Check contain one element}} \newline System.out.println(names.contains("harry")); //true \newline  \newline - {\bf{Check contain multiple elements}} \newline System.out.println(names.containsAll(List.of("harry", "john"))); //true \newline  \newline -{}-{}-{}-{}-{}-{}-{}-{}-{}-{}-{}-{}-{}-{}-{}-{}-{}-{}-{}-{}-{}-{}-{}-{}-{}-{}-{}-{}-{}-{}-{}-{}-{}-{}-{}-{}-{}-{}-{}-- \newline  \newline Collection\textless{}String\textgreater{} names = new ArrayList\textless{}\textgreater{}(List.of("john", "james", "harry")); \newline  \newline - {\bf{Convert to array with array type}} \newline String{[}{]} strings = names.toArray(new String{[}{]}\{\}); \newline System.out.println(Arrays.toString(strings)); //{[}john, james, harry{]}} \tn 
\hhline{>{\arrayrulecolor{DarkBackground}}-}
\end{tabularx}
\par\addvspace{1.3em}

\begin{tabularx}{8.4cm}{X}
\SetRowColor{DarkBackground}
\mymulticolumn{1}{x{8.4cm}}{\bf\textcolor{white}{Set}}  \tn
\SetRowColor{white}
\mymulticolumn{1}{x{8.4cm}}{- No duplicates \newline % Row Count 1 (+ 1)
- Order is not significant \newline % Row Count 2 (+ 1)
- No more methods than Collection interface \newline % Row Count 3 (+ 1)
• Don't care order → HashSet \newline % Row Count 4 (+ 1)
• Keep insertion order → LinkedHashSet \newline % Row Count 5 (+ 1)
• Store Enum in a Set → EnumSet \newline % Row Count 6 (+ 1)
• When need multi-thread, size small, read more – less write → CopyOnWriteArraySet \newline % Row Count 8 (+ 2)
• Auto sort element → TreeSet \newline % Row Count 9 (+ 1)
• When need multi-thread + Auto sort → ConcurrentSkipListSet% Row Count 11 (+ 2)
} \tn 
\hhline{>{\arrayrulecolor{DarkBackground}}-}
\end{tabularx}
\par\addvspace{1.3em}

\begin{tabularx}{8.4cm}{X}
\SetRowColor{DarkBackground}
\mymulticolumn{1}{x{8.4cm}}{\bf\textcolor{white}{Set Methods}}  \tn
\SetRowColor{LightBackground}
\mymulticolumn{1}{x{8.4cm}}{- {\bf{Create a set}} \newline Set\textless{}String\textgreater{} uniqueNames = new HashSet\textless{}\textgreater{}(); \newline  \newline - {\bf{Create an unmodified set}} \newline Set\textless{}String\textgreater{} uniqueNames = Set.of("b", "a", "c"); \newline System.out.println(uniqueNames); //{[}a, b, c{]} \newline  \newline - {\bf{Create a set from a list}} \newline Set\textless{}String\textgreater{} uniqueNames = new HashSet\textless{}\textgreater{}(List.of("a", "b", "a", "c")); \newline System.out.println(uniqueNames); //{[}a, b, c{]}} \tn 
\hhline{>{\arrayrulecolor{DarkBackground}}-}
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\par\addvspace{1.3em}

\begin{tabularx}{8.4cm}{X}
\SetRowColor{DarkBackground}
\mymulticolumn{1}{x{8.4cm}}{\bf\textcolor{white}{List}}  \tn
\SetRowColor{white}
\mymulticolumn{1}{x{8.4cm}}{- A collection in which order is significant \newline % Row Count 1 (+ 1)
- Allow duplicate elements \newline % Row Count 2 (+ 1)
• Insert and get element fast → ArrayList \newline % Row Count 3 (+ 1)
• Insert and remove fast → LinkedList \newline % Row Count 4 (+ 1)
• When need multi-thread → CopyOnWriteArrayList% Row Count 6 (+ 2)
} \tn 
\hhline{>{\arrayrulecolor{DarkBackground}}-}
\end{tabularx}
\par\addvspace{1.3em}

\begin{tabularx}{8.4cm}{X}
\SetRowColor{DarkBackground}
\mymulticolumn{1}{x{8.4cm}}{\bf\textcolor{white}{List Methods}}  \tn
\SetRowColor{LightBackground}
\mymulticolumn{1}{x{8.4cm}}{List contains all methods that defines in collection interface,  \newline and some methods work with index \newline  \newline -{}-{}-{}-{}-{}-{}-{}-{}-{}-{}-{}-{}-{}-{}-{}-{}-{}-{}-{}-{}-{}-{}-{}-{}-{}-{}-{}-{}-{}-{}-{}-{}-{}-{}-{}-{}-{}-{}-{}-{}-{}-{}-{}-{}-{}-{}-{}-{}- \newline  \newline List\textless{}String\textgreater{} chars = new ArrayList\textless{}\textgreater{}(List.of("a", "b", "c")); \newline  \newline - {\bf{Add an element at position}} \newline chars.add(2, "new"); \newline System.out.println(chars); //{[}a, b, new, c{]} \newline  \newline - {\bf{Add multiple elements at position}} \newline chars.addAll(2, List.of("newA", "newB")); \newline System.out.println(chars); //{[}a, b, newA, newB, c{]} \newline  \newline - {\bf{Edit an element at position}} \newline chars.set(2, "newA"); \newline System.out.println(chars); //{[}a, b, newA{]} \newline  \newline - {\bf{Get an element at position}} \newline System.out.println(chars.get(0)); //a \newline  \newline - {\bf{Check index of an element}} \newline System.out.println(chars.indexOf("b")); //1 \newline  \newline - {\bf{Remove an element at position}} \newline chars.remove(1); \newline System.out.println(chars); //{[}a, c{]} \newline  \newline -{}-{}-{}-{}-{}-{}-{}-{}-{}-{}-{}-{}-{}-{}-{}-{}-{}-{}-{}-{}-{}-{}-{}-{}-{}-{}-{}-{}-{}-{}-{}-{}-{}-{}-{}-{}-{}-{}-{}-{}-{}-{}-{}-{}-{}-{}-{}-{}- \newline  \newline - {\bf{Create an unmodified list}} \newline List\textless{}String\textgreater{} chars = List.of("a", "b", "c"); \newline  \newline - {\bf{Create list from an unmodified list}} \newline List\textless{}String\textgreater{} chars = new ArrayList\textless{}\textgreater{}(List.of("a", "b", "c")); \newline  \newline - {\bf{Sort a list a -{}-\textgreater{} z}} \newline List\textless{}String\textgreater{} chars = new ArrayList\textless{}\textgreater{}(List.of("b", "a", "c")); \newline chars.sort(Comparator.naturalOrder()); \newline System.out.println(chars); //{[}a, b, c{]} \newline  \newline - {\bf{Sort a list z -{}-\textgreater{} a}} \newline chars.sort(Comparator.reverseOrder()); \newline System.out.println(chars); //{[}c, b, a{]} \newline  \newline - {\bf{Replace/Update all elements}} \newline List\textless{}String\textgreater{} chars = new ArrayList\textless{}\textgreater{}(List.of("a", "b", "c")); \newline chars.replaceAll(s -\textgreater{} s + "\_1"); \newline System.out.println(chars); //{[}a\_1, b\_1, c\_1{]}} \tn 
\hhline{>{\arrayrulecolor{DarkBackground}}-}
\end{tabularx}
\par\addvspace{1.3em}

\begin{tabularx}{8.4cm}{X}
\SetRowColor{DarkBackground}
\mymulticolumn{1}{x{8.4cm}}{\bf\textcolor{white}{Map}}  \tn
\SetRowColor{white}
\mymulticolumn{1}{x{8.4cm}}{- key-value associations to store and retrieve elements \newline % Row Count 2 (+ 2)
• Normal map → HashMap \newline % Row Count 3 (+ 1)
• Keep insertion order → LinkedHashMap \newline % Row Count 4 (+ 1)
• Key is Enum → EnumMap \newline % Row Count 5 (+ 1)
• Auto sort → TreeMap \newline % Row Count 6 (+ 1)
• When multi-thread → ConcurrentHashMap% Row Count 7 (+ 1)
} \tn 
\hhline{>{\arrayrulecolor{DarkBackground}}-}
\end{tabularx}
\par\addvspace{1.3em}

\begin{tabularx}{8.4cm}{X}
\SetRowColor{DarkBackground}
\mymulticolumn{1}{x{8.4cm}}{\bf\textcolor{white}{Map Methods}}  \tn
\SetRowColor{LightBackground}
\mymulticolumn{1}{x{8.4cm}}{Some methods to work with map \newline  \newline -{}-{}-{}-{}-{}-{}-{}-{}-{}-{}-{}-{}-{}-{}-{}-{}-{}-{}-{}-{}-{}-{}-{}-{}-{}-{}-{}-{}-{}-{}-{}-{}-{}-{}-{}-{}-{}-{}- \newline  \newline - {\bf{Create an normal map}} \newline Map\textless{}Integer, String\textgreater{} names = new HashMap\textless{}\textgreater{}(); \newline Map\textless{}String, Person\textgreater{} names = new HashMap\textless{}\textgreater{}(); \newline  \newline - {\bf{Create an unmodified map}} \newline Map\textless{}Integer, String\textgreater{} names = Map.of(1, "john", 2, "james"); \newline  \newline - {\bf{Create a modified map from an unmodified map}} \newline Map\textless{}Integer, String\textgreater{} names = new HashMap\textless{}\textgreater{}(Map.of(1, "john", 2, "james")); \newline  \newline -{}-{}-{}-{}-{}-{}-{}-{}-{}-{}-{}-{}-{}-{}-{}-{}-{}-{}-{}-{}-{}-{}-{}-{}-{}-{}-{}-{}-{}-{}-{}-{}-{}-{}-{}-{}-{}-{}- \newline  \newline Map\textless{}Integer, String\textgreater{} names = new HashMap\textless{}\textgreater{}(); \newline  \newline - {\bf{Add one element}} \newline names.put(1, "john"); \newline System.out.println(names); //\{1=john\} \newline  \newline - {\bf{Add multiple elements}} \newline names.putAll(Map.of(1, "john", 2, "james")); \newline System.out.println(names); //\{1=john, 2=james\} \newline  \newline - {\bf{Get value by key}} \newline String name = names.get(1); \newline System.out.println(name); //john \newline  \newline - {\bf{Get value by key, if don't exist return default value}} \newline String name = names.getOrDefault(3, "NOT\_FOUND"); \newline System.out.println(name); //NOT\_FOUND \newline  \newline -{}-{}-{}-{}-{}-{}-{}-{}-{}-{}-{}-{}-{}-{}-{}-{}-{}-{}-{}-{}-{}-{}-{}-{}-{}-{}-{}-{}-{}-{}-{}-{}-{}-{}-{}-{}-{}-{}- \newline  \newline Map\textless{}Integer, String\textgreater{} names = new HashMap\textless{}\textgreater{}(Map.of(1, "john", 2, "james")); \newline  \newline - {\bf{Get all keys}} \newline Set\textless{}Integer\textgreater{} keys = names.keySet(); \newline System.out.println(keys); //{[}1, 2{]} \newline  \newline - {\bf{Get all values}} \newline Collection\textless{}String\textgreater{} values = names.values(); \newline System.out.println(values); //{[}john, james{]} \newline  \newline - {\bf{Print key-value}} \newline names.forEach((k, v) -\textgreater{} System.out.printf("k=\%s, v=\%s \%n", k, v)); \newline //k=1, v=john  \newline //k=2, v=james  \newline -{}-{}-{}-{}-{}-{}-{}-{}-{}-{}-{}-{}-{}-{}-{}-{}-{}-{}-{}-{}-{}-{}-{}-{}-{}-{}-{}-{}-{}-{}-{}-{}-{}-{}-{}-{}-{}-{}- \newline  \newline - {\bf{Update multiple values}} \newline Map\textless{}Integer, String\textgreater{} names = new HashMap\textless{}\textgreater{}(); \newline for (int i = 0; i \textless{} 4; i++) \{ \newline     names.compute(i, (k, v) -\textgreater{} "john\_" + k); \newline \} \newline System.out.println(names); // \{0=john\_0, 1=john\_1, 2=john\_2, 3=john\_3\}} \tn 
\hhline{>{\arrayrulecolor{DarkBackground}}-}
\end{tabularx}
\par\addvspace{1.3em}


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

\end{document}