From 5056f162e30f49aa2b0a906d4ecb72772129fe9b Mon Sep 17 00:00:00 2001
From: "Dr. Martin Goik" <goik@hdm-stuttgart.de>
Date: Thu, 21 May 2020 13:43:47 +0200
Subject: [PATCH] Enhanced X-Mas tree solution
---
.../Ref/Statements/MoreFunXmasTree/pom.xml | 76 +++
.../java/de/hdm_stuttgart/mi/sd1/Dummy.java | 25 +
.../java/de/hdm_stuttgart/mi/sd1/Xmas.java | 90 +++
.../hdm_stuttgart/mi/sd1/XmasUsingFormat.java | 53 ++
Doc/Sd1/statements.xml | 515 ++++++++++++------
5 files changed, 595 insertions(+), 164 deletions(-)
create mode 100644 Doc/Sd1/Ref/Statements/MoreFunXmasTree/pom.xml
create mode 100644 Doc/Sd1/Ref/Statements/MoreFunXmasTree/src/main/java/de/hdm_stuttgart/mi/sd1/Dummy.java
create mode 100644 Doc/Sd1/Ref/Statements/MoreFunXmasTree/src/main/java/de/hdm_stuttgart/mi/sd1/Xmas.java
create mode 100644 Doc/Sd1/Ref/Statements/MoreFunXmasTree/src/main/java/de/hdm_stuttgart/mi/sd1/XmasUsingFormat.java
diff --git a/Doc/Sd1/Ref/Statements/MoreFunXmasTree/pom.xml b/Doc/Sd1/Ref/Statements/MoreFunXmasTree/pom.xml
new file mode 100644
index 000000000..af1a514e8
--- /dev/null
+++ b/Doc/Sd1/Ref/Statements/MoreFunXmasTree/pom.xml
@@ -0,0 +1,76 @@
+<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+ xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
+ <modelVersion>4.0.0</modelVersion>
+
+ <groupId>de.hdm_stuttgart.mi.sd1</groupId>
+ <artifactId>morefunxmastree</artifactId>
+ <version>0.9</version>
+ <packaging>jar</packaging>
+
+ <name>morefunxmastree</name>
+
+ <url>https://freedocs.mi.hdm-stuttgart.de/sd1_sect_mavenCli.html</url>
+
+ <description>Exercise »More fun with Xmas trees«.</description>
+
+ <properties>
+ <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
+ </properties>
+
+ <build>
+ <plugins>
+
+ <plugin>
+ <groupId>org.apache.maven.plugins</groupId>
+ <artifactId>maven-compiler-plugin</artifactId>
+ <version>3.8.1</version>
+ <configuration>
+ <source>11</source>
+ <target>11</target>
+ </configuration>
+ </plugin>
+
+ <plugin>
+ <groupId>org.apache.maven.plugins</groupId>
+ <artifactId>maven-javadoc-plugin</artifactId>
+ <version>3.1.1</version>
+ <configuration>
+ <linksource>true</linksource>
+ <additionalOptions>
+ <additionalOption>-html5</additionalOption>
+ </additionalOptions>
+ <javadocExecutable>${java.home}/bin/javadoc</javadocExecutable>
+ </configuration>
+ </plugin>
+
+ <plugin>
+ <groupId>org.apache.maven.plugins</groupId>
+ <artifactId>maven-shade-plugin</artifactId>
+ <version>3.2.1</version>
+ <configuration>
+ <transformers>
+ <transformer
+ implementation="org.apache.maven.plugins.shade.resource.ManifestResourceTransformer">
+ <manifestEntries>
+ <Main-Class>de.hdm_stuttgart.mi.sd1.App</Main-Class>
+ </manifestEntries>
+ </transformer>
+ </transformers>
+ </configuration>
+ <executions>
+ <execution>
+ <phase>package</phase>
+ <goals>
+ <goal>shade</goal>
+ </goals>
+ </execution>
+ </executions>
+ </plugin>
+ <plugin>
+ <groupId>org.apache.maven.plugins</groupId>
+ <artifactId>maven-site-plugin</artifactId>
+ <version>3.7.1</version>
+ </plugin>
+ </plugins>
+ </build>
+</project>
diff --git a/Doc/Sd1/Ref/Statements/MoreFunXmasTree/src/main/java/de/hdm_stuttgart/mi/sd1/Dummy.java b/Doc/Sd1/Ref/Statements/MoreFunXmasTree/src/main/java/de/hdm_stuttgart/mi/sd1/Dummy.java
new file mode 100644
index 000000000..164929c3f
--- /dev/null
+++ b/Doc/Sd1/Ref/Statements/MoreFunXmasTree/src/main/java/de/hdm_stuttgart/mi/sd1/Dummy.java
@@ -0,0 +1,25 @@
+package de.hdm_stuttgart.mi.sd1;
+
+public class Dummy {
+ public static void main(String[] args) {
+ System.out.print("\""); // Print a double quote "
+ System.out.print("Hello\n"); // Print 'Hello' followed by a new line.
+ System.out.print("\t Hello â£"); // Print an indented 'Hello' string.
+ System.out.println("\u2B95"); // Print a unicode right arrow ⮕
+
+
+
+ final int numberOfRowGroups = 5;
+ System.out.format("%"+ numberOfRowGroups + "s ", "\\ /");
+
+ System.out.println();
+ final int repetitions = 3;
+ System.out.println("/_".repeat(repetitions));
+
+ System.out.println();
+ final int numberOfSpaces = 6;
+ System.out.format("%"+ numberOfSpaces + "s ", "");
+ System.out.print(":");
+ }
+
+}
diff --git a/Doc/Sd1/Ref/Statements/MoreFunXmasTree/src/main/java/de/hdm_stuttgart/mi/sd1/Xmas.java b/Doc/Sd1/Ref/Statements/MoreFunXmasTree/src/main/java/de/hdm_stuttgart/mi/sd1/Xmas.java
new file mode 100644
index 000000000..b8da23880
--- /dev/null
+++ b/Doc/Sd1/Ref/Statements/MoreFunXmasTree/src/main/java/de/hdm_stuttgart/mi/sd1/Xmas.java
@@ -0,0 +1,90 @@
+package de.hdm_stuttgart.mi.sd1;
+
+/**
+ * Beginner's way of implementing the »More fun with X-mas trees« exercise.
+ */
+public class Xmas {
+
+ public static void main(String[] args) {
+
+ // Example: 5 row groups, tree body's loop index ranging from 0 to 4
+
+ // \ / Part 1: Printing tree's top.
+ // -->*<--
+ // /_\
+ // Row group index 0 /_\_\ Part 2: Tree's body, printing
+ // /_/_/_\ two lines per group index
+ // Row group index 1 /_\_\_\ loop iteration.
+ // /_/_/_/_\
+ // Row group index 2 /_\_\_\_\
+ // /_/_/_/_/_\
+ // Row group index 3 /_\_\_\_\_\
+ // /_/_/_/_/_/_\
+ // Row group index 4 /_\_\_\_\_\_\ End of tree's body
+ // /_/_/_/_/_/_/_\
+ // [___] Part 3: Bottom trunk line.
+
+ final int numberOfRowGroups = 5; // You may easily change this
+ // parameter.
+ // Printing tree's top
+ //
+
+ // Tree's top first line
+ for (int x = 0; x < numberOfRowGroups + 1; x++) { // Printing the tree's "\ /"
+ // top. We need numberOfRows+1
+ System.out.print(' '); // preceding spaces before
+ } // eventually printing the
+ System.out.println("\\ /"); // "\ /" String.
+
+ // Tree's top second line
+ for (int x = 0; x < numberOfRowGroups - 1; x++) { // Printing the tree's top '-->*<--'
+ // We need numberOfRows-1
+ System.out.print(' '); // preceding spaces
+ } // before printing the
+ System.out.println("-->*<--"); // "-->*<--" string.
+
+ // Tree's top third line
+ for (int x = 0; x < numberOfRowGroups + 1; x++) { // The tree's lower top "/ \" line.
+ System.out.print(' '); // Again we need numberOfRowGroups+1
+ } // preceding spaces.
+ System.out.println("/_\\");
+
+ // Part two: The tree's body
+ //
+ for (int rowGroup = 0; // Outer loop printing the
+ rowGroup < numberOfRowGroups; rowGroup++) { // tree's body.
+
+ // First body line of current group
+ //
+ for (int x = 0; // Starting first line
+ x < numberOfRowGroups - rowGroup;x++) { // of row group with
+ // (numberOfRows - row)
+ System.out.print(' '); // space characters ...
+ }
+ System.out.print("/"); // Start of current row group's
+ for (int x = 0; x < rowGroup + 2;x++) { // first line tree body content
+ System.out.print("_\\"); // finishing.
+ }
+ System.out.println();
+
+ // Second body line of current group
+ //
+ for (int x = 0; // Starting second line of row
+ x < numberOfRowGroups - rowGroup - 1; x++) { // group with (numberOfRows -
+ System.out.print(' '); // row - 1) space characters ...
+ }
+ for (int x = 0; x < rowGroup + 3;x++) { // tree body content
+ System.out.print("/_");
+ }
+ System.out.println("\\"); // finishing.
+ }
+
+ // Part three: The tree's bottom trunk
+ //
+ for (int x = 0; x < numberOfRowGroups; x++) { // Indenting the bottom trunk ...
+ System.out.print(' ');
+ }
+ System.out.println("[___]"); // printing the trunk.
+ }
+
+}
diff --git a/Doc/Sd1/Ref/Statements/MoreFunXmasTree/src/main/java/de/hdm_stuttgart/mi/sd1/XmasUsingFormat.java b/Doc/Sd1/Ref/Statements/MoreFunXmasTree/src/main/java/de/hdm_stuttgart/mi/sd1/XmasUsingFormat.java
new file mode 100644
index 000000000..8722cd82f
--- /dev/null
+++ b/Doc/Sd1/Ref/Statements/MoreFunXmasTree/src/main/java/de/hdm_stuttgart/mi/sd1/XmasUsingFormat.java
@@ -0,0 +1,53 @@
+package de.hdm_stuttgart.mi.sd1;
+
+
+/**
+ * Simplified implementation replacing loops by {@link java.io.PrintStream#format(String, Object...)} and
+ * {@link String#repeat(int)}.
+ */
+public class XmasUsingFormat {
+
+ public static void main(String[] args) {
+
+ // Example: 5 row groups, tree body's loop index ranging from 0 to 4
+
+ // \ / Part 1: Printing tree's top.
+ // -->*<--
+ // /_\
+ // Row group index 0 /_\_\ Part 2: Tree's body, printing
+ // /_/_/_\ two lines per group index
+ // Row group index 1 /_\_\_\ loop iteration.
+ // /_/_/_/_\
+ // Row group index 2 /_\_\_\_\
+ // /_/_/_/_/_\
+ // Row group index 3 /_\_\_\_\_\
+ // /_/_/_/_/_/_\
+ // Row group index 4 /_\_\_\_\_\_\ End of tree's body
+ // /_/_/_/_/_/_/_\
+ // [___] Part 3: Bottom trunk line.
+
+ final int numberOfRowGroups = 5; // You may easily change this parameter.
+
+ // Printing the tree's top
+ System.out.format("%"+ (numberOfRowGroups + 5) + "s\n", "\\ /");
+ System.out.format("%"+ (numberOfRowGroups + 7) + "s\n", "-->*<--");
+ System.out.format("%"+ (numberOfRowGroups + 5) + "s\n", "/_\\");
+
+ // Printing the tree's body
+
+ // Loop printing the tree's body row group wise.
+ for (int rowGroup = 0; rowGroup < numberOfRowGroups; rowGroup++) {
+
+ // First body line of current group
+ System.out.format("%"+ (numberOfRowGroups + rowGroup + 6) + "s\n", "/" + "_\\".repeat(rowGroup + 2));
+
+ // Second body line of current group
+ System.out.format
+ ("%"+ (numberOfRowGroups + rowGroup + 6) + "s\\\n",
+ "/_".repeat(rowGroup + 3));
+ }
+ // Printing the tree's trunk
+ System.out.format("%"+ (numberOfRowGroups + 6) + "s\n", "[___]");
+ }
+
+}
diff --git a/Doc/Sd1/statements.xml b/Doc/Sd1/statements.xml
index 6cd304c3f..a7cdefbf6 100644
--- a/Doc/Sd1/statements.xml
+++ b/Doc/Sd1/statements.xml
@@ -2802,185 +2802,372 @@ for (int row = 0; row < numberOfRows; row++) {
</question>
<answer>
- <para>We start from a version being fully covered by our current
- knowledge:</para>
+ <para>A complete solution is available at the <link
+ xlink:href="https://gitlab.mi.hdm-stuttgart.de/goik/GoikLectures/-/tree/master/Doc/Sd1/Ref/Statements/MoreFunXmasTree/src/main/java/de/hdm_stuttgart/mi/sd1/Xmas.java">MI
+ Gitlab</link> repository. We start from a version being fully
+ covered by our current knowledge by dissecting the problem. Our
+ aim is to print the following lines:</para>
+
+ <programlisting language="none"> <emphasis
+ role="red">\ /</emphasis> <emphasis role="red">Part 1: Printing tree's top.</emphasis>
+ <emphasis role="red">-->*<--</emphasis>
+ <emphasis role="red">/_\</emphasis>
+Row group index 0 /_\_\ Part 2: Tree's body, printing
+ /_/_/_\ two lines per group index
+Row group index 1 /_\_\_\ loop iteration.
+ /_/_/_/_\
+Row group index 2 /_\_\_\_\
+ /_/_/_/_/_\
+Row group index 3 /_\_\_\_\_\
+ /_/_/_/_/_/_\
+Row group index 4 /_\_\_\_\_\_\ End of tree's body
+ /_/_/_/_/_/_/_\
+ <emphasis role="red">[___]</emphasis> <emphasis
+ role="red">Part 3: Bottom trunk line.</emphasis></programlisting>
+
+ <para>For each row group albeit having different length the two
+ patterns <code>"/_\_ ... \_\"</code> and <code>"/_/ ...
+ /_\"</code> keep repeating. Like in the previous exercises we
+ need the precise indentation values for <abbrev>e.g.</abbrev>
+ starting the tree's body. The following output shows two trees
+ of different sizes showing invisible spaces by <quote>â£</quote>.
+ In the »bigger« tree's first line we need <abbrev>e.g.</abbrev>
+ 6 spaces before actually printing the tree's very top "<emphasis
+ role="red"><code>\/</code></emphasis>".</para>
+
+ <programlisting language="none"> A tree with A tree with
+ 5 row groups 2 row groups
+
+â£â£â£â£â£â£<emphasis role="red">\ /</emphasis> â£â£â£<emphasis
+ role="red">\ /</emphasis>
+â£â£â£â£<emphasis role="red">-->*<--</emphasis> â£<emphasis
+ role="red">-->*<--</emphasis>
+â£â£â£â£â£â£<emphasis role="red">/_\</emphasis> â£â£â£<emphasis
+ role="red">/_\</emphasis>
+â£â£â£â£â£/_\_\ â£â£/_\_\
+â£â£â£â£/_/_/_\ â£/_/_/_\
+â£â£â£â£/_\_\_\ â£/_\_\_\
+â£â£â£/_/_/_/_\ /_/_/_/_\
+â£â£â£/_\_\_\_\ â£â£<emphasis role="red">[___]</emphasis>
+â£â£/_/_/_/_/_\
+â£â£/_\_\_\_\_\
+â£/_/_/_/_/_/_\
+â£/_\_\_\_\_\_\
+/_/_/_/_/_/_/_\
+â£â£â£â£â£<emphasis role="red">[___]</emphasis></programlisting>
+
+ <para>The precise amounts of these indentations obviously depend
+ on the tree's size. Printing larger trees requires larger
+ indentation values. The tree's size is being controlled by the
+ parameter <parameter>numberOfRowGroups</parameter>:</para>
+
+ <programlisting language="java">final int numberOfRowGroups = 5;</programlisting>
+
+ <para>Now we start printing the tree's top <code>"\/"</code>.
+ Printing <emphasis role="red"><code>\</code></emphasis> in <xref
+ linkend="glo_Java"/> is surprisingly difficult since the
+ backslash character is being used to escape double quotes,
+ newline, tab, <productname>Unicode</productname> and other
+ characters within strings:</para>
+
+ <programlisting language="none">System.out.print("<emphasis
+ role="red">\"</emphasis>"); // Print a double quote <emphasis
+ role="red">"</emphasis>
+System.out.print("Hello<emphasis role="red">\n</emphasis>"); // Print 'Hello' followed by a <emphasis
+ role="red">new line</emphasis>.
+System.out.print("<emphasis role="red">\t</emphasis> Hello"); // Print a <emphasis
+ role="red">tab indented</emphasis> 'Hello' string.
+System.out.println("<emphasis role="red">\u2B95</emphasis>"); // Print a unicode right arrow <emphasis
+ role="red">⮕</emphasis>
+
+System.out.print("<emphasis role="red">\\</emphasis>"); // Print a single backslash <emphasis
+ role="red">\</emphasis> character</programlisting>
+
+ <para>The above snippet shows a solution: Within a given string
+ the backslash character must itself be escaped by a second one
+ to get a single backslash character on output. In addition we
+ need preceding spaces (â£) being represented by the space <code>'
+ '</code> character.</para>
+
+ <para>Printing our tree's very top thus requires:</para>
- <programlisting language="java">public static void main(String[] args) {
+ <informaltable border="0">
+ <col width="80%"/>
- // Example: 5 row groups, tree's body loop index ranging from 0 to 4
-
- // \ / The tree's top.
- // -->*<--
- // /_\
- // 0 /_\_\ Start of tree's body
- // /_/_/_\
- // 1 /_\_\_\
- // /_/_/_/_\
- // 2 /_\_\_\_\
- // /_/_/_/_/_\
- // 3 /_\_\_\_\_\
- // /_/_/_/_/_/_\
- // 4 /_\_\_\_\_\_\
- // /_/_/_/_/_/_/_\ End of tree's body
- // [___] Bottom trunk line.
-
-
- final int numberOfRowGroups = 5; // You may easily change this
- // value.
- // Part one: The tree's top
- //
- for (int x = 0; x < numberOfRowGroups + 1; x++) { // Printing the tree's very
- // top. We need numberOfRows+1
- System.out.print(' '); // preceding spaces
- } // before printing the
- System.out.println("\\ /"); // "\ /" String.
-
- for (int x = 0; x < numberOfRowGroups - 1; x++) { // Printing the tree's top '*'
- // We need numberOfRows-1
- System.out.print(' '); // preceding spaces
- } // before printing the
- System.out.println("-->*<--"); // "-->*<--" string.
-
- for (int x = 0; x < numberOfRowGroups + 1; x++) { // The tree's lower top "/ \".
- System.out.print(' '); // We need again numberOfRows+1
- } // preceding spaces.
- System.out.println("/_\\");
+ <col width="20%"/>
- // Part two: The tree's body
- //
- for (int rowGroup = 0; // Outer loop printing the
- rowGroup < numberOfRowGroups; rowGroup++) { // tree's body.
+ <tr>
+ <th>Code</th>
- // First body line of current group
- //
- for (int x = 0; // Starting first line
- x < numberOfRowGroups - rowGroup;x++) { // of row group with
+ <th>Result</th>
+ </tr>
+
+ <tr>
+ <td valign="top"><programlisting language="none">for (int x = 0; x < numberOfRowGroups + 1; x++) { // Printing the tree's "\ /" top. We need
+ System.out.print(' '); // numberOfRowGroups+1 preceding spaces (â£)
+} // before eventually printing the
+System.out.println("<emphasis role="red">\\ /</emphasis>"); // "<emphasis
+ role="red">\ /</emphasis>" String followed by a newline (print<emphasis
+ role="red">ln</emphasis>).</programlisting></td>
+
+ <td valign="top"><screen>â£â£â£â£â£â£<emphasis role="red">\ /</emphasis> </screen><para>(<quote>â£</quote>
+ denoting space)</para></td>
+ </tr>
+ </informaltable>
+
+ <para>As you'll probably realize the expression
+ <code>numberOfRowGroups + 1</code> equals 6 in case of 5 row
+ groups like in the illustration given before. Printing our
+ tree's top next two of lines is straightforward:</para>
+
+ <informaltable border="0">
+ <col width="80%"/>
+
+ <col width="20%"/>
+
+ <tr>
+ <th>Code</th>
+
+ <th>Result</th>
+ </tr>
+
+ <tr>
+ <td valign="top"><programlisting language="none">for (int x = 0; x < numberOfRowGroups - 1; x++) { // Printing the tree's top '-->*<--' we
+ System.out.print(' '); // need numberOfRows-1 preceding spaces (â£)
+} // before printing the "<emphasis
+ role="red">-->*<--</emphasis>"
+System.out.println("<emphasis role="red">-->*<--</emphasis>"); // string.
+
+for (int x = 0; x < numberOfRowGroups + 1; x++) { // The tree's lower top "<emphasis
+ role="red">/ \</emphasis>":
+ System.out.print(' '); // We need another numberOfRows+1
+} // preceding spaces (â£).
+System.out.println("<emphasis role="red">/_\\</emphasis>");</programlisting></td>
+
+ <td valign="top"><screen>â£â£â£â£â£â£\ /
+â£â£â£â£<emphasis role="red">-->*<--</emphasis>
+â£â£â£â£â£â£<emphasis role="red">/ \</emphasis></screen></td>
+ </tr>
+ </informaltable>
+
+ <para>We now turn to the tree's body. Following the idea of row
+ groups each consisting of two lines we require:</para>
+
+ <programlisting language="none">for (int rowGroup = 0; rowGroup < numberOfRowGroups; rowGroup++) {
+
+ // print first row of group e.g. <emphasis role="red">/_\_\</emphasis>
+ // print second row of group <emphasis role="red">/_/_/_\</emphasis>
+
+}</programlisting>
+
+ <para>We now show the loop's gory details:</para>
+
+ <informaltable border="0">
+ <col width="80%"/>
+
+ <col width="20%"/>
+
+ <tr>
+ <th>Code</th>
+
+ <th>Result</th>
+ </tr>
+
+ <tr>
+ <td valign="top"><programlisting language="none">for (int rowGroup = 0; // Outer loop printing the
+ rowGroup < numberOfRowGroups; rowGroup++) { // tree's body.
+
+ // First body line of current group
+ //
+ for (int x = 0; // Starting first line
+ x < numberOfRowGroups - rowGroup;x++) { // of row group with
// (numberOfRows - row)
- System.out.print(' '); // space characters ...
- }
- System.out.print("/"); // Start of current row group's
- for (int x = 0; x < rowGroup + 2;x++) { // first line tree body content
- System.out.print("_\\"); // finishing.
- }
- System.out.println();
-
- // Second body line of current group
- //
- for (int x = 0; // Starting second line of row
- x < numberOfRowGroups - rowGroup - 1; x++) { // group with (numberOfRows -
- System.out.print(' '); // row - 1) space characters ...
- }
- for (int x = 0; x < rowGroup + 3;x++) { // tree body content
- System.out.print("/_");
- }
- System.out.println("\\"); // finishing.
+ System.out.print(' '); // space (â£) characters
+ }
+ System.out.print("<emphasis role="red">/</emphasis>"); // Start of current row group's
+ for (int x = 0; x < rowGroup + 2;x++) { // first line tree body content
+ System.out.print("<emphasis role="red">_\\</emphasis>"); // finishing.
}
+ System.out.println();
- // Part three: The tree's bottom trunk
+ // Second body line of current group
//
- for (int x = 0; x < numberOfRowGroups; x++) { // Indenting the bottom trunk ...
- System.out.print(' ');
+ for (int x = 0; // Starting second line of row
+ x < numberOfRowGroups - rowGroup - 1; x++) { // group with (numberOfRows -
+ System.out.print(' '); // row - 1) space (â£) characters
}
- System.out.println("[___]"); // printing the trunk.
-}</programlisting>
+ for (int x = 0; x < rowGroup + 3;x++) { // tree body content
+ System.out.print("<emphasis role="red">/_</emphasis>");
+ }
+ System.out.println("<emphasis role="red">\\</emphasis>"); // finishing.
+}</programlisting></td>
- <para>This solution is a bit cumbersome: It involves a repeating
- task namely indenting lines by a given amount of spaces.</para>
-
- <para>So far we have not yet introduced methods. In anticipation
- of <link linkend="sd1SectClassMembers">class methods</link> we
- provide an alternate solution introducing a method
- <methodname>printIndented(...)</methodname> printing a given
- string a configurable number of times being indented by a given
- number of whitespace characters. This method uses <package
- xlink:href="https://docs.oracle.com/javase/10/docs/api/java/lang/System.html">System</package>.<parameter
- xlink:href="https://docs.oracle.com/javase/10/docs/api/java/lang/System.html#out">out</parameter>.<methodname
- xlink:href="https://docs.oracle.com/javase/10/docs/api/java/io/PrintStream.html#format(java.lang.String,java.lang.Object...)">format(...)</methodname>
- as in <xref
- linkend="sd1QandaSquareNumberTableFormatted"/>.</para>
-
- <para>Using <methodname>printIndented(...)</methodname>
- considerable enhances our code's readability. We do no longer
- need the <quote>inner</quote> loops. On the downside fiddling
- with values describing indentations and repetitions is still
- being required:</para>
-
- <programlisting language="java">public class XmasTree {
-
- // Helper method.
- //
- // Print string s a number of times defined by the repeat value being preceded by a number
- // of whitespace characters ' ' given by the indentation value.
- // Thus printIndent(5, "axb", 2) will generate "_____axbaxb" with "_" denoting white space.
- //
- private static void printIndent(final int indentation, final String s, final int repeat) {
- if (0 < indentation) {
- final String format = "%" + indentation + "s";
- System.out.format(format, "");
- }
- for (int i = 0; i < repeat; i++) {
- System.out.print(s);
- }
- }
+ <td valign="top"><screen>â£â£â£â£â£â£\ /
+â£â£â£â£-->*<--
+â£â£â£â£â£â£/ \
+â£â£â£â£â£<emphasis role="red">/_\_\</emphasis>
+â£â£â£â£<emphasis role="red">/_/_/_\</emphasis>
+â£â£â£â£<emphasis role="red">/_\_\_\</emphasis>
+â£â£â£<emphasis role="red">/_/_/_/_\</emphasis>
+â£â£â£<emphasis role="red">/_\_\_\_\</emphasis>
+â£â£<emphasis role="red">/_/_/_/_/_\</emphasis>
+â£â£<emphasis role="red">/_\_\_\_\_\</emphasis>
+â£<emphasis role="red">/_/_/_/_/_/_\</emphasis>
+â£<emphasis role="red">/_\_\_\_\_\_\</emphasis>
+<emphasis role="red">/_/_/_/_/_/_/_\</emphasis></screen></td>
+ </tr>
+ </informaltable>
- public static void main(String[] args) {
+ <para>Finally printing the tree's trunk:</para>
- // Example: 5 row groups of two lines each, tree's body loop index ranging from 0 to 4
- //
- // Each groups consists of two lines having identical structure among all groups:
- // Group n: /_\_\ ... _\ «/» followed by repeating «_\» n+2 times
- // /_/_ ... /_\ Repeating «/_» n+3 times ending with «\»
-
- // \ / The tree's top.
- // -->*<--
- // /_\
- // 0 /_\_\ Start of tree's body
- // /_/_/_\
- // 1 /_\_\_\
- // /_/_/_/_\
- // 2 /_\_\_\_\
- // /_/_/_/_/_\
- // 3 /_\_\_\_\_\
- // /_/_/_/_/_/_\
- // 4 /_\_\_\_\_\_\
- // /_/_/_/_/_/_/_\ End of tree's body
- // [___] Bottom trunk line.
-
-
- final int numberOfRowGroups = 5; // You may easily change this value.
-
- // Part one: The tree's top
- //
- printIndent(numberOfRowGroups + 1, "\\ /\n" ,1);
- printIndent(numberOfRowGroups - 1, "-->*<--\n",1);
- printIndent(numberOfRowGroups + 1, "/_\\\n" ,1);
-
- // Part two: The tree's body
- //
- for (int rowGroup = 0; // Outer loop printing the
- rowGroup < numberOfRowGroups; rowGroup++) { // tree's body group by group.
-
- printIndent(numberOfRowGroups - rowGroup,"/", 1);// Starting first line of group
- printIndent(0,"_\\", rowGroup + 2); // print leaves
- System.out.println(); // Finishing first line of group.
-
- // Second body line of current group
- //
- printIndent(numberOfRowGroups - rowGroup - 1, "", 1); // Starting second line
- printIndent(0, "/_", rowGroup + 3); // of row group
-
- System.out.println("\\"); // Finish second line of group.
- }
+ <informaltable border="0">
+ <col width="80%"/>
- // Part three: The tree's bottom trunk
- //
- printIndent (numberOfRowGroups, "[___]", 1); // Indenting the bottom trunk ...
- }
-}</programlisting>
+ <col width="20%"/>
+
+ <tr>
+ <th>Code</th>
+
+ <th>Result</th>
+ </tr>
+
+ <tr>
+ <td valign="top"><programlisting language="none">// Part three: The tree's bottom trunk
+//
+for (int x = 0; x < numberOfRowGroups; x++) { // Indenting the bottom trunk ...
+ System.out.print(' ');
+}
+System.out.println("<emphasis role="red">[___]</emphasis>"); // printing the trunk.</programlisting></td>
+
+ <td valign="top"><screen>â£â£â£â£â£â£\ /
+â£â£â£â£-->*<--
+â£â£â£â£â£â£/ \
+â£â£â£â£â£/_\_\
+â£â£â£â£/_/_/_\
+â£â£â£â£/_\_\_\
+â£â£â£/_/_/_/_\
+â£â£â£/_\_\_\_\
+â£â£/_/_/_/_/_\
+â£â£/_\_\_\_\_\
+â£/_/_/_/_/_/_\
+â£/_\_\_\_\_\_\
+/_/_/_/_/_/_/_\
+â£â£â£â£â£<emphasis role="red">[___]</emphasis></screen></td>
+ </tr>
+ </informaltable>
+
+ <para>So far quite an amount of energy has been invested into
+ printing fixed numbers of space characters using loop
+ statements. The
+ <classname>System</classname><code>.</code><property>out</property><code>.</code><methodname
+ xlink:href="https://docs.oracle.com/en/java/javase/14/docs/api/java.base/java/io/PrintStream.html#format(java.lang.String,java.lang.Object...)">format()</methodname>
+ method as in <xref
+ linkend="sd1QandaSquareNumberTableFormatted"/> allows for
+ getting rid of these loops completely. As an example printing
+ the tree's top simplifies to:</para>
+
+ <informaltable border="0">
+ <col width="70%"/>
+
+ <col width="30%"/>
+
+ <tr>
+ <th>Indenting using loops</th>
+
+ <th>Common result</th>
+ </tr>
+
+ <tr>
+ <td valign="top"><programlisting language="java">for (int x = 0; x < numberOfRowGroups + 1; x++) {
+ System.out.print(' ');
+}
+System.out.println("\\ /"); </programlisting></td>
+
+ <td rowspan="3" valign="top"><screen>â£â£â£â£â£â£\ /</screen></td>
+ </tr>
+
+ <tr>
+ <th>Indenting using format()</th>
+ </tr>
+
+ <tr>
+ <td valign="top"><programlisting>System.out.format("%"+ numberOfRowGroups + "s ", "\\ /");</programlisting></td>
+ </tr>
+ </informaltable>
+
+ <para>Moreover starting with <xref linkend="glo_Java"/> 11 the
+ <classname
+ xlink:href="https://docs.oracle.com/en/java/javase/14/docs/api/java.base/java/lang/String.html">String</classname>
+ class features a <methodname
+ xlink:href="https://docs.oracle.com/en/java/javase/14/docs/api/java.base/java/lang/String.html#repeat(int)">repeat()</methodname>
+ method:</para>
+
+ <informaltable border="0">
+ <col width="70%"/>
+
+ <col width="30%"/>
+
+ <tr>
+ <th>String repetitions using loops</th>
+
+ <th>Common result</th>
+ </tr>
+
+ <tr>
+ <td valign="top"><programlisting language="none">final int repetitions = 3;
+for (int i = 0; i < repetitions; i++) {
+ System.out.print("/_");
+}</programlisting></td>
+
+ <td rowspan="3" valign="top"><screen>/_/_/_</screen></td>
+ </tr>
+
+ <tr>
+ <th>Using <methodname
+ xlink:href="https://docs.oracle.com/en/java/javase/14/docs/api/java.base/java/lang/String.html#repeat(int)">repeat()</methodname>
+ instead</th>
+ </tr>
+
+ <tr>
+ <td valign="top"><programlisting>final int repetitions = 3;
+System.out.println("/_".repeat(repetitions));</programlisting></td>
+ </tr>
+ </informaltable>
+
+ <para>Combining both methods completely obsoletes all
+ <quote>inner</quote> loops thereby considerably enhancing our
+ code's readability as being shown in the <link
+ xlink:href="https://gitlab.mi.hdm-stuttgart.de/goik/GoikLectures/-/tree/master/Doc/Sd1/Ref/Statements/MoreFunXmasTree/src/main/java/de/hdm_stuttgart/mi/sd1/XmasUsingFormat.java">XmasUsingFormat</link>
+ implementation.</para>
+
+ <programlisting language="java">final int numberOfRowGroups = 5; // You may easily change this parameter.
+
+// Printing the tree's top
+System.out.format("%"+ (numberOfRowGroups + 5) + "s\n", "\\ /");
+System.out.format("%"+ (numberOfRowGroups + 7) + "s\n", "-->*<--");
+System.out.format("%"+ (numberOfRowGroups + 5) + "s\n", "/_\\");
+
+// Printing the tree's body
+
+// Loop printing the tree's body row group wise.
+for (int rowGroup = 0; rowGroup < numberOfRowGroups; rowGroup++) {
+
+ // First body line of current group
+ System.out.format("%"+ (numberOfRowGroups + rowGroup + 6) + "s\n", "/" + "_\\".repeat(rowGroup + 2));
+
+ // Second body line of current group
+ System.out.format
+ ("%"+ (numberOfRowGroups + rowGroup + 6) + "s\\\n",
+ "/_".repeat(rowGroup + 3));
+ }
+// Printing the tree's trunk
+System.out.format("%"+ (numberOfRowGroups + 6) + "s\n", "[___]");
+</programlisting>
- <para>Both variants allow for setting e.g. <code
+ <para>Both implementation variants allow for setting e.g. <code
language="java">final int numberOfRowGroups = 8</code> creating
- a larger tree (albeit having the same trunk size):</para>
+ trees of different sizes albeit sharing the same trunk
+ size:</para>
<screen> \ /
-->*<--
--
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