Gradle custom tasks to compile with different Java versions

build.gradle.kts

plugins {
    id("java")
}

tasks.register("compileOn11", JavaCompile::class.java) {
    javaCompiler = javaToolchains.compilerFor {
        languageVersion = JavaLanguageVersion.of(11)
    }
    source = sourceSets["main"].allSource.asFileTree
    classpath = sourceSets["main"].compileClasspath
    destinationDirectory.set(file("build/classes/java/main/11"))
}

tasks.register("compileOn17", JavaCompile::class.java) {
    javaCompiler = javaToolchains.compilerFor {
        languageVersion = JavaLanguageVersion.of(17)
    }
    source = sourceSets["main"].allSource.asFileTree
    classpath = sourceSets["main"].compileClasspath
    destinationDirectory.set(file("build/classes/java/main/17"))
}

tasks.register("compileOn21", JavaCompile::class.java) {
    javaCompiler = javaToolchains.compilerFor {
        languageVersion = JavaLanguageVersion.of(21)
    }
    source = sourceSets["main"].allSource.asFileTree
    classpath = sourceSets["main"].compileClasspath
    destinationDirectory.set(file("build/classes/java/main/21"))
}