import org.gradle.jvm.toolchain.internal.SpecificInstallationToolchainSpec;

import javax.annotation.Nullable;

public class JavadocExecutableUtils {

    @Nullable
    public static JavaToolchainSpec getExecutableOverrideToolchainSpec(Javadoc task, ObjectFactory objectFactory) {
        String customExecutable = task.getExecutable();
        if (customExecutable != null) {

import javax.annotation.Nullable;
import java.io.File;

public class JavaCompileExecutableUtils {

    @Nullable
    public static JavaToolchainSpec getExecutableOverrideToolchainSpec(JavaCompile task, ObjectFactory objectFactory) {
        if (!task.getOptions().isFork()) {
            return null;
        }

        ForkOptions forkOptions = task.getOptions().getForkOptions();

import org.gradle.jvm.toolchain.internal.SpecificInstallationToolchainSpec;

import javax.annotation.Nullable;

public class JavaExecExecutableUtils {

    @Nullable
    public static JavaToolchainSpec getExecutableOverrideToolchainSpec(JavaExec task, ObjectFactory objectFactory) {
        String customExecutable = task.getExecutable();
        if (customExecutable != null) {

            javaCompile.setSource(javaSource);

            Provider<JavaToolchainSpec> toolchainOverrideSpec = project.provider(() ->
                JavaCompileExecutableUtils.getExecutableOverrideToolchainSpec(javaCompile, objectFactory));
            javaCompile.getJavaCompiler().convention(getToolchainTool(project, JavaToolchainService::compilerFor, toolchainOverrideSpec));

            ObjectFactory objectFactory = project.getObjects();
            Provider<JavaToolchainSpec> toolchainOverrideSpec = project.provider(() ->
                JavaExecExecutableUtils.getExecutableOverrideToolchainSpec(run, objectFactory));
            run.getJavaLauncher().convention(getToolchainTool(project, JavaToolchainService::launcherFor, toolchainOverrideSpec));
        });
    }

        JavaToolchainService javaToolchainService = getJavaToolchainService();
        Provider<JavaLauncher> javaLauncherConvention = getProviderFactory()
            .provider(() -> JavaExecExecutableUtils.getExecutableOverrideToolchainSpec(this, objectFactory))
            .flatMap(javaToolchainService::launcherFor)
            .orElse(javaToolchainService.launcherFor(it -> {}));

        JavaToolchainService javaToolchainService = getJavaToolchainService();
        Provider<JavaCompiler> javaCompilerConvention = getProviderFactory()
            .provider(() -> JavaCompileExecutableUtils.getExecutableOverrideToolchainSpec(this, objectFactory))
            .flatMap(javaToolchainService::compilerFor)
            .orElse(javaToolchainService.compilerFor(it -> {}));

        JavaToolchainService javaToolchainService = getJavaToolchainService();
        Provider<JavadocTool> javadocToolConvention = getProviderFactory()
            .provider(() -> JavadocExecutableUtils.getExecutableOverrideToolchainSpec(this, objectFactory))
            .flatMap(javaToolchainService::javadocToolFor)
            .orElse(javaToolchainService.javadocToolFor(it -> {}));