Sample code explaining differences between sealed classes and interfaces in Java and Kotlin.
- Kotlin Sealed Classes: https://kotlinlang.org/docs/sealed-classes.html
- Java Sealed Classes: https://openjdk.java.net/jeps/409
code without sealed classes (source):
fun verifyGithubOrganization(gitHub: GitHub, org: String): GHOrganization? {
return try {
gitHub.getOrganization(org)
} catch (ioe: IOException) {
null
}
}usage (source):
val githubOrganization = Utils.verifyGithubOrganization(github, organizationName)
githubOrganization?.let {
val repositories = Utils.listOrgRepos(it, limit = -1)
repositories.forEach { println("repo: ${it.name}") }
}similar code with sealed classes (source):
fun verifyGithubOrganization(gitHub: GitHub, org: String): Organization {
return try {
Organization.Success(gitHub.getOrganization(org))
} catch (ioe: IOException) {
Organization.Failure(ioe.localizedMessage)
}
}usage (source):
when (org) {
is Organization.Success -> listOrgRepos(org.githubOrg, limit)
is Organization.Failure -> emptyList()
}code without sealed class (source):
public static List<GHRepository> listRepositories(GHOrganization gitHubOrganization){
try {
return gitHubOrganization.listRepositories().toList();
} catch (IOException ioe) {
return null;
}
}usage (source):
List<GHRepository> repos = Utils.listRepositories(gitHubOrganizationSuccess.ghOrganization());
if (repos != null) {
repos.forEach(repo -> System.out.println(repo.getName().toLowerCase()));
}similar code with sealed classes (source):
public static GitHubRepository listRepos(GHOrganization gitHubOrganization){
try {
return new GitHubRepositorySuccess(gitHubOrganization.listRepositories().toList());
} catch (IOException ioe) {
return new GitHubRepositoryFailure(ioe.getLocalizedMessage());
}
}similar code with sealed interfaces and records (source):
public static GitHubRepository listGitHubRepositories(GHOrganization gitHubOrganization){
try {
return new GitHubRepositorySuccess(gitHubOrganization.listRepositories().toList());
} catch (IOException ioe) {
return new GitHubRepositoryFailure(ioe.getLocalizedMessage());
}
}usage with Java 17 (Preview) language level (source)
GitHubOrganization githubOrganization = Utils.verifyGithubOrganization(gitHub, organizationName);
switch (githubOrganization) {
case GitHubOrganizationSuccess gitHubOrganizationSuccess -> {
List<GHRepository> repos = Utils.listRepositories(gitHubOrganizationSuccess.ghOrganization());
repos.forEach(repo -> System.out.println(repo.getName().toLowerCase()));
}
case GitHubOrganizationFailure gitHubOrganizationFailure -> {
System.out.println(gitHubOrganizationFailure.error());
}
}usage with plain java 17:
if (gitHubRepository instanceof GitHubRepositorySuccess gitHubRepositorySuccess){
return gitHubRepositorySuccess.ghRepositories();
} else if (gitHubConnectionResult instanceof GitHubConnectionFailure gitHubConnectionFailure) {
System.out.println("gitHubConnectionFailure.getError(): " + gitHubConnectionFailure.getError());
} else {
return 1;
}Create a github personal access token with at least the following scopes:
Java and Kotlin code reads GitHub organization data provided by the -o flag
cd kotlin
export GITHUB_OAUTH=<your github personal access token>
./gradlew clean build && java -jar app/build/dist/app.jar -o [GitHub organization to read repositories from]cd java
export GITHUB_OAUTH=<your github personal access token>
./gradlew clean build && java --enable-preview -jar app/build/dist/app.jar -o [GitHub organization to read repositories from]
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