用Java中的流API调用替换for-each循环

Question

Having this code:

public Map<Job, Collection<JobTransform>> getPartitioning() {
    Map<Job, Collection<JobTransform>> partitioning = new IdentityHashMap<>();
    for (JobTransform jobTransform : content) {
        Job job = jobTransform.getJob();
        Collection<JobTransform> collection = partitioning.get(job);
        if (collection == null) {
           collection = new LinkedList<>();
           partitioning.put(job, collection);
        }
        collection.add(jobTransform);
    }
    return partitioning;
}

and 'content' being a constructor parameter for the class this method is implemented in, how can I convert the for-each loop into code using Stream API in Java? For now I have only

content.stream().map(JobTransform::getJob)

and I don't know how can I use each job further. Do I use the API wrong? Please help me to improve my code!

Answer 1

content.stream().collect(Collectors.groupingBy(JobTransform::getJob, IdentityHashMap::new, Collectors.toCollection(LinkedList::new)));

这将与您的非流代码完全一样。