Initial commit of library, unit tests, and pom file.

.classpath

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+<?xml version="1.0" encoding="UTF-8"?>
+<classpath>
+	<classpathentry kind="src" path="src/main/java"/>
+	<classpathentry kind="src" path="src/test/java"/>
+	<classpathentry kind="con" path="org.eclipse.jdt.launching.JRE_CONTAINER/org.eclipse.jdt.internal.debug.ui.launcher.StandardVMType/java-11-openjdk-amd64">
+		<attributes>
+			<attribute name="module" value="true"/>
+		</attributes>
+	</classpathentry>
+	<classpathentry kind="con" path="org.eclipse.jdt.junit.JUNIT_CONTAINER/5"/>
+	<classpathentry kind="output" path="bin"/>
+</classpath>

.project

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+<?xml version="1.0" encoding="UTF-8"?>
+<projectDescription>
+	<name>PublicSuffixList</name>
+	<comment></comment>
+	<projects>
+	</projects>
+	<buildSpec>
+		<buildCommand>
+			<name>org.eclipse.jdt.core.javabuilder</name>
+			<arguments>
+			</arguments>
+		</buildCommand>
+	</buildSpec>
+	<natures>
+		<nature>org.eclipse.jdt.core.javanature</nature>
+	</natures>
+</projectDescription>

.settings/org.eclipse.jdt.core.prefs

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+eclipse.preferences.version=1
+org.eclipse.jdt.core.compiler.codegen.inlineJsrBytecode=enabled
+org.eclipse.jdt.core.compiler.codegen.methodParameters=do not generate
+org.eclipse.jdt.core.compiler.codegen.targetPlatform=9
+org.eclipse.jdt.core.compiler.codegen.unusedLocal=preserve
+org.eclipse.jdt.core.compiler.compliance=9
+org.eclipse.jdt.core.compiler.debug.lineNumber=generate
+org.eclipse.jdt.core.compiler.debug.localVariable=generate
+org.eclipse.jdt.core.compiler.debug.sourceFile=generate
+org.eclipse.jdt.core.compiler.problem.assertIdentifier=error
+org.eclipse.jdt.core.compiler.problem.enumIdentifier=error
+org.eclipse.jdt.core.compiler.source=9

README.md

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+Public Suffix List Helper
+-------------------------
+
+##### Terminology used in this page:
+
+* TLD   - Top Level Domain
+* SLD   - Second Level Domain
+* eTLD  - effective Top Level Domain
+* ccSLD - country-code Second Level Domain
+
+The Public Suffix List is a register of domain suffixes that are used in
+combination to provide effective Top Level Domains for certain actual Top
+Level Domains.
+
+For example, the TLD .uk has a number of second-level domains that are for most
+purposes considered part of the TLD. Therefore, .co.uk, .ac.uk, .org.uk can all
+be thought of as eTLDs, made up of a ccTLD and an actual TLD.
+
+```
+	Host    SLD        ccSLD    TLD
+	-------------------------------
+	www     example             com
+	www     example    co       uk
+```
+
+Above, the eTLDs would be '.com' and '.co.uk'.
+
+In the `net.susa.cfs.psl` package, I consider the part to the left of the eTLD to
+be the SLD. Everything to the left of the SLD is taken as the host.
+
+To achieve this, we load the Public Suffix List into a tree structure. The
+first tree level contains the actual TLDs, each of which contains a list of
+their ccSLDs, each of which can contain further ccSLDs, and so on.
+
+```
+                   root
+                    |
+         -----------------------
+         |                     |
+         uk                    au
+         |                     |
+     ----------         -------------------
+     |   |    |         |                 |
+    co  ac   org       edu               gov
+                        |                 |
+                     -------------     -------
+                     |     |     |     |     |
+                    vic   wa    tas   vic   wa
+```
+
+Using a tree allows us to store and search the list of ~9000 entries quickly
+when processing large numbers of URLs.
+
+The API to check a URL for is: -
+
+	String getETLD(String fqdn)
+
+Returns the substring that should be considered the TLD. If the domain does not
+match any entry from the Public Suffix List, then the first part of the domain
+is returned. If the string cannot be parsed as a valid domain, the function
+returns the empty string.
+

pom.xml

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+<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/maven-v4_0_0.xsd">
+
+  <modelVersion>4.0.0</modelVersion>
+
+  <groupId>net.susa.cfs.psl</groupId>
+  <artifactId>PublicSuffixList</artifactId>
+
+  <packaging>jar</packaging>
+
+  <version>1.0-SNAPSHOT</version>
+
+  <name>PublicSuffixList</name>
+  <url>http://maven.apache.org</url>
+
+  <properties>
+    <maven.compiler.source>1.9</maven.compiler.source>
+    <maven.compiler.target>1.9</maven.compiler.target>
+  </properties>
+
+  <dependencies>
+    <dependency>
+        <groupId>org.junit.jupiter</groupId>
+        <artifactId>junit-jupiter-api</artifactId>
+        <version>5.3.2</version>
+        <scope>test</scope>
+    </dependency>
+    <dependency>
+        <groupId>org.junit.jupiter</groupId>
+        <artifactId>junit-jupiter-engine</artifactId>
+        <version>5.3.2</version>
+        <scope>test</scope>
+    </dependency>
+  </dependencies>
+
+  <build>
+	<plugins>
+		<plugin>
+			<groupId>org.apache.maven.plugins</groupId>
+			<artifactId>maven-compiler-plugin</artifactId>
+			<version>3.8.0</version>
+		</plugin>
+		<plugin>
+			<groupId>org.apache.maven.plugins</groupId>
+			<artifactId>maven-surefire-plugin</artifactId>
+			<version>2.22.0</version>
+			<configuration>
+				<argLine>
+					--illegal-access=permit
+				</argLine>
+			</configuration>
+		</plugin>
+		<plugin>
+			<groupId>org.apache.maven.plugins</groupId>
+			<artifactId>maven-failsafe-plugin</artifactId>
+			<version>2.22.0</version>
+			<configuration>
+				<argLine>
+					--illegal-access=permit
+				</argLine>
+			</configuration>
+		</plugin>
+	</plugins>
+  </build>
+</project>