多个线程在Java中调用相同的方法

我的代码使用两个线程来调用相同的方法，但是该程序仅将第一个线程运行两次，而不是第二个线程，而且我不太确定为什么会这样。

ParallelImplementation(String repoPath1, String repoPath2, int revisions) throws IOException, GitAPIException {
    git1 = Git.open(new File(repoPath1));
    repo1 = FileRepositoryBuilder.create(new File(repoPath1));
    git2 = Git.open(new File(repoPath2));
    repo2 = FileRepositoryBuilder.create(new File(repoPath2));
    allCommits1 = getAllCommits(git1);
    allCommits2 = getAllCommits(git2);
    childParentMap1 = getParentCommit(allCommits1);
    childParentMap2 = getParentCommit(allCommits2);
    mapIterator1 = childParentMap1.entrySet().iterator();
    mapIterator2 = childParentMap2.entrySet().iterator();
    ExecutorService pool1 = Executors.newFixedThreadPool(N_THREADS);
    ExecutorService pool2 = Executors.newFixedThreadPool(N_THREADS);
    new Thread(() -> {
        try {
            runParallelImplementation(repoPath1, pool1, git1, repo1, allCommits1, childParentMap1, mapIterator1);
        } catch (GitAPIException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
    }).start();
    new Thread(() -> {
        try {
            runParallelImplementation(repoPath1, pool2, git2, repo2, allCommits2, childParentMap2, mapIterator2);
        } catch (GitAPIException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
    }).start();
}