initial commit

Author: ParadoxV5

.github/workflows/packages.yml

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+name: GitHub Packages
+on: {release: {types: [published]}}
+jobs:
+  packages:
+    runs-on: ubuntu-latest
+    timeout-minutes: 2
+    steps:
+    
+    - uses: actions/checkout@v3
+    
+    - uses: actions/setup-java@v3
+      with:
+        distribution: temurin
+        java-version: '17'
+        cache: maven
+        server-id: github
+    
+    - name: Package with Maven
+      run: mvn -batch-mode package --file pom.xml
+    
+    - name: Publish to GitHub Packages
+      run: mvn deploy
+      env: {GITHUB_TOKEN: "${{github.token}}"}

.gitignore

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+# JetBrains
+/.idea/
+
+# Java
+/target/

LICENSE.txt

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+Boost Software License - Version 1.0 - August 17th, 2003
+
+Permission is hereby granted, free of charge, to any person or organization
+obtaining a copy of the software and accompanying documentation covered by
+this license (the "Software") to use, reproduce, display, distribute,
+execute, and transmit the Software, and to prepare derivative works of the
+Software, and to permit third-parties to whom the Software is furnished to
+do so, all subject to the following:
+
+The copyright notices in the Software and this entire statement, including
+the above license grant, this restriction and the following disclaimer,
+must be included in all copies of the Software, in whole or in part, and
+all derivative works of the Software, unless such copies or derivative
+works are solely in the form of machine-executable object code generated by
+a source language processor.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE, TITLE AND NON-INFRINGEMENT. IN NO EVENT
+SHALL THE COPYRIGHT HOLDERS OR ANYONE DISTRIBUTING THE SOFTWARE BE LIABLE
+FOR ANY DAMAGES OR OTHER LIABILITY, WHETHER IN CONTRACT, TORT OR OTHERWISE,
+ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
+DEALINGS IN THE SOFTWARE.

README.md

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+# `MyString`
+
+A Java
+[`CharSequence`](https://docs.oracle.com/en/java/javase/17/docs/api/java.base/java/lang/CharSequence.html)
+implementation backed by a
+[`Character`](https://docs.oracle.com/en/java/javase/17/docs/api/java.base/java/lang/Character.html)
+[`List`](https://docs.oracle.com/en/java/javase/17/docs/api/java.base/java/util/List.html)
+
+The backing list determines whether the instance is mutable (i.e. writeable).
+
+
+## About
+
+This is the difference between `CharSequence` and
+[`String`](https://docs.oracle.com/en/java/javase/17/docs/api/java.base/java/lang/String.html)
+in a concrete piece of code.
+
+I originally prepared this to keep my Java experience fresh, but as the project develops,
+[JetBrains annotations](https://github.com/JetBrains/java-annotations),
+[Maven (`pom.xml`)](https://maven.apache.org/pom.html) and
+[GitHub Actions & Packages](https://docs.github.com/en/actions/publishing-packages/publishing-java-packages-with-maven#publishing-packages-to-github-packages)
+joined the party too. 
+
+
+## License
+
+Copyright ParadoxV5 2022. Distributed under the
+[Boost Software License, Version 1.0](https://www.boost.org/users/license.html).

pom.xml

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+<?xml version="1.0" encoding="UTF-8" ?>
+<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>xyz.paradoxv5</groupId>
+  <artifactId>mystring</artifactId>
+  <name>mystring</name>
+  <version>1.0</version>
+  
+  <developers><developer>
+    <id>ParadoxV5</id>
+    <url>https://github.com/ParadoxV5/</url>
+  </developer></developers>
+  <licenses><license>
+    <name>BSL-1.0</name>
+    <comments>Boost Software License 1.0</comments>
+    <url>https://www.boost.org/users/license.html</url>
+  </license></licenses>
+  
+  <build>
+    <sourceDirectory>src</sourceDirectory>
+    <testSourceDirectory>test</testSourceDirectory>
+    <plugins><plugin>
+      <groupId>org.apache.maven.plugins</groupId>
+      <artifactId>maven-compiler-plugin</artifactId>
+      <version>3.10.1</version>
+      <configuration><release>17</release></configuration>
+    </plugin></plugins>
+  </build>
+  <properties><project.build.sourceEncoding>UTF-8</project.build.sourceEncoding></properties>
+  
+  <dependencies><dependency>
+    <groupId>org.jetbrains</groupId>
+    <artifactId>annotations</artifactId>
+    <version>23.0.0</version>
+  </dependency></dependencies>
+  
+  <scm>
+    <developerConnection>scm:git:https://github.com/ParadoxV5/java-mystring.git</developerConnection>
+    <url>https://github.com/ParadoxV5/java-mystring</url>
+  </scm>
+  <distributionManagement><repository>
+    <id>github</id>
+    <name>GitHub Packages</name>
+    <url>https://maven.pkg.github.com/ParadoxV5/java-mystring</url>
+  </repository></distributionManagement>
+  
+</project>

src/xyz/paradoxv5/MyString.java

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+package xyz.paradoxv5;
+import org.jetbrains.annotations.*;
+import java.util.*;
+
+/**
+  A {@link CharSequence} implementation backed by {@linkplain #chars a Character List}
+  <p>
+  The backing list determines whether the instance is mutable (i.e. writeable).
+  
+  @author
+    <a href="https://github.com/ParadoxV5/">ParadoxV5</a>.
+    <a href="https://www.boost.org/LICENSE_1_0.txt">Boost Software License 1.0</a>
+  @version
+    {@value #serialVersionUID}.0
+*/
+public class MyString implements CharSequence, Comparable<@NotNull CharSequence>, Cloneable, java.io.Serializable {
+  @java.io.Serial private static final long serialVersionUID = 1;
+  
+  private @NotNull List<Character> chars;
+  @Contract(value = "-> _", pure = true)
+  public @NotNull List<Character> getChars() { return chars; }
+  @Contract(mutates="this")
+  public void setChars(@NotNull List<Character> chars) { this.chars = Objects.requireNonNull(chars); }
+  @Contract(mutates="this")
+  public MyString(@NotNull List<Character> chars) { this.chars = Objects.requireNonNull(chars); }
+  
+  @Contract(mutates="this") public MyString(@NotNull CharSequence charSeq) {
+    this(charSeq instanceof MyString myString
+      ? myString.getChars()
+      : charSeq.chars().mapToObj(e -> Character.valueOf((char)e)).toList()
+    );
+  }
+  @Contract(mutates="this") public MyString(char @NotNull... charArray) {
+    this(String.valueOf(charArray));
+  }
+  
+  @Contract(value = "_ -> _", pure = true) @Override
+  public char charAt(int index) { return getChars().get(index).charValue(); }
+  @Contract(value = "-> _", pure = true) @Override
+  public int length() { return getChars().size(); }
+  @Contract(value = "_, _ -> new", pure = true) @Override
+  public MyString subSequence(int start, int end) { return new MyString(getChars().subList(start, end)); }
+  @Contract(value = "_ -> _", pure = true) @Override
+  public int compareTo(@NotNull CharSequence other) { return CharSequence.compare(this, other); }
+  
+  @Contract(value = "-> new", pure = true) public char @NotNull[] toCharArray() {
+    List<Character> chars = getChars();
+    char[] charArray = new char[chars.size()];
+    @NotNull ListIterator<Character> iter = chars.listIterator();
+    while(iter.hasNext())
+      charArray[iter.nextIndex()] = iter.next().charValue();
+    return charArray;
+  }
+  @Contract(value = "-> _", pure = true) @Override public @NotNull String toString() {
+    return String.valueOf(toCharArray());
+  }
+  @Contract(value = "-> new", pure = true) public MyString deepClone() {
+    return new MyString(new LinkedList<>(getChars()));
+  }
+  
+  @Contract(value = "null -> false; !null -> _", pure = true) @Override
+  public boolean equals(@Nullable Object obj) {
+    return super.equals(obj)
+      || obj instanceof MyString other
+      && getChars().equals(other.getChars());
+  }
+  @Contract(value = "-> _", pure = true) @Override public int hashCode() {
+    return getChars().hashCode();
+  }
+  @Contract(value = "-> new", pure = true) @Override
+  public @NotNull MyString clone() throws CloneNotSupportedException { return (MyString)(super.clone()); }
+}