From d0b4a9114b270fc3fe11ea3d9307872b613ae0ec Mon Sep 17 00:00:00 2001
From: Martin Goik <goik@hdm-stuttgart.de>
Date: Wed, 29 Nov 2017 11:11:17 +0100
Subject: [PATCH] Reference types
---
Doc/Sd1/objectsClasses.xml | 178 ++++++++++++++++++++++++++++++++++++-
1 file changed, 177 insertions(+), 1 deletion(-)
diff --git a/Doc/Sd1/objectsClasses.xml b/Doc/Sd1/objectsClasses.xml
index 9f5bc07c6..3d651a8ae 100644
--- a/Doc/Sd1/objectsClasses.xml
+++ b/Doc/Sd1/objectsClasses.xml
@@ -4040,7 +4040,6 @@ public class <link
balance = balance * Math.pow((1 + defaultInterestRate / 100), years) ;
}
}</programlisting>
-
</answer>
</qandaentry>
</qandadiv>
@@ -8189,6 +8188,183 @@ sin(4 * PI)=4518.2187229323445, difference=4518.2187229323445</screen>
</section>
</section>
+ <section xml:id="sda1_sect_valueVsReferenceType">
+ <title>Value types and reference types</title>
+
+ <figure xml:id="sd1_fig_valueRefType">
+ <title>Value vs. reference types</title>
+
+ <glosslist>
+ <glossentry>
+ <glossterm>Value type</glossterm>
+
+ <glossdef>
+ <para>Holding data within own memory location.</para>
+
+ <para>Eight value types in <xref linkend="glo_Java"/>:
+ <code>byte</code>, <code>short</code>, <code>int</code>,
+ <code>long</code>, <code>float</code>, <code>double</code>,
+ <code>char</code> and <code>boolean</code>.</para>
+ </glossdef>
+ </glossentry>
+
+ <glossentry>
+ <glossterm>Reference type</glossterm>
+
+ <glossdef>
+ <para>All class instances i.e. <classname>String</classname>,
+ <classname>java.util.Scanner</classname> etc.</para>
+ </glossdef>
+ </glossentry>
+ </glosslist>
+ </figure>
+
+ <figure xml:id="sd1_fig_valueRefExample">
+ <title>Example</title>
+
+ <informaltable border="1">
+ <colgroup width="76%"/>
+
+ <colgroup width="24%"/>
+
+ <tr>
+ <td valign="top"><programlisting language="java">int a = 1;
+int b = a;
+a = 5;
+System.out.println(
+ "a="+a+"\nb=" + b);</programlisting></td>
+
+ <td valign="top"><screen>a=5
+b=1 </screen></td>
+ </tr>
+
+ <tr>
+ <td valign="top"><programlisting language="java">StringBuffer r = new StringBuffer("Joe");
+StringBuffer s = r;
+r.append(" Simpson");
+
+System.out.println("r="+r+"\ns="+s);</programlisting></td>
+
+ <td valign="top"><screen>r=Joe Simpson
+s=Joe Simpson </screen></td>
+ </tr>
+ </informaltable>
+ </figure>
+
+ <figure xml:id="sd1_fig_callByValueExample">
+ <title><emphasis>Only</emphasis> »call-by-value« in <xref
+ linkend="glo_Java"/></title>
+
+ <informaltable border="1">
+ <colgroup width="69%"/>
+
+ <colgroup width="31%"/>
+
+ <tr>
+ <td valign="top"><programlisting language="java">public static void main(String[] args) {
+ int value = 3;
+ System.out.println("Before printDuplicateValue: " + value);
+ printDuplicateValue(value);
+ System.out.println("After printDuplicateValue: " + value);
+}
+static void printDuplicateValue(int n) {
+ n = 2 * n;
+ System.out.println("printDuplicateValue: " + n);
+}</programlisting></td>
+
+ <td valign="top"><screen>Before printDuplicateValue: <emphasis
+ role="red">3</emphasis>
+printDuplicateValue: <emphasis role="red">6</emphasis>
+After printDuplicateValue: <emphasis role="red">3</emphasis></screen></td>
+ </tr>
+ </informaltable>
+ </figure>
+
+ <figure xml:id="sd1_fig_callByValueStringBuffer">
+ <title><emphasis>»call-by-reference« for objects?</emphasis></title>
+
+ <informaltable border="1">
+ <colgroup width="66%"/>
+
+ <colgroup width="34%"/>
+
+ <tr>
+ <td valign="top"><programlisting language="java">public static void main(String[] args) {
+ StringBuffer buffer = new StringBuffer("My");
+ System.out.println("Before duplicateString: " + buffer);
+ duplicateString(buffer);
+ System.out.println("After duplicateString: " + buffer);
+
+}
+static void duplicateString(StringBuffer b) {
+ b.append(b); // Append self
+}</programlisting></td>
+
+ <td valign="top"><screen>Before duplicateString: <emphasis
+ role="red">My</emphasis>
+After duplicateString: <emphasis role="red">MyMy </emphasis></screen></td>
+ </tr>
+ </informaltable>
+ </figure>
+
+ <figure xml:id="sd1_fig_NoCallByReferenceInJava">
+ <title><emphasis>No »call-by-reference« in <xref
+ linkend="glo_Java"/></emphasis></title>
+
+ <informaltable border="1">
+ <colgroup width="66%"/>
+
+ <colgroup width="34%"/>
+
+ <tr>
+ <td valign="top"><programlisting language="java">public static void main(String[] args) {
+ StringBuffer buffer = new StringBuffer("My");
+ System.out.println("Before duplicateString: " + buffer);
+ replaceString(buffer);
+ System.out.println("After duplicateString: " + buffer);
+}
+static void replaceString(StringBuffer b) {
+ b = new StringBuffer("Replacement");
+}</programlisting></td>
+
+ <td valign="top"><screen>Before duplicateString: <emphasis
+ role="red">My</emphasis>
+After duplicateString: <emphasis role="red">My</emphasis></screen></td>
+ </tr>
+ </informaltable>
+ </figure>
+
+ <figure xml:id="sd1_fig_CallByReferenceCpp">
+ <title><emphasis>C++ offers <quote>true</quote>
+ »call-by-reference«</emphasis></title>
+
+ <informaltable border="1">
+ <colgroup width="69%"/>
+
+ <colgroup width="31%"/>
+
+ <tr>
+ <td valign="top"><programlisting language="none">void printDuplicateValue(int<emphasis
+ role="red">&</emphasis> n) { // alternate name
+ n = 2 * n;
+ cout << "printDuplicateValue: " << n << endl;
+}
+int main() {
+ int value = 3;
+ cout << "Before printDuplicateValue: " << value << endl;
+ printDuplicateValue(value);
+ cout << "Before printDuplicateValue: " << value << endl;
+}</programlisting></td>
+
+ <td valign="top"><screen>Before printDuplicateValue: <emphasis
+ role="red">3</emphasis>
+printDuplicateValue: <emphasis role="red">6</emphasis>
+After printDuplicateValue: <emphasis role="red">6</emphasis></screen></td>
+ </tr>
+ </informaltable>
+ </figure>
+ </section>
+
<section xml:id="set_sd1_methodCallingDetails">
<title>Method calls, the details</title>
--
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