The URL you are using to post, is not correct, the url should have the Blog Id,the format of the url is:
http://www.blogger.com/feeds/BLOG_ID/posts/default
So in java, you can do this as follows:
GoogleService myService = new GoogleService("blogger", "exampleCo-exampleApp-1");
myService.setUserCredentials("EMAIL", "PWD");
Entry myEntry = new Entry();
myEntry.setTitle(new PlainTextConstruct("TITLE post update"));
myEntry.setContent(new PlainTextConstruct("STATUS POST"));
URL feedUrl = new URL("http://www.blogger.com/feeds/default/blogs");
Feed resultFeed = myService.getFeed(feedUrl, Feed.class);
String blog_name = "blog_name"; //the name of the blog where you want to post status
String BLOG_ID = "";
for (int i = 0; i < resultFeed.getEntries().size(); i++) {
Entry entry = resultFeed.getEntries().get(i);
if (entry.getTitle().getPlainText().equalsIgnoreCase(blog_name)) {
String[] split = entry.getId().split("-");
BLOG_ID = split[split.length - 1];
}
System.out.println("Posting to:" + " " + "Blog id: " + BLOG_ID + " " + "Blog name: " + blog_name);
}
URL postUrl = new URL("http://www.blogger.com/feeds/" + BLOG_ID + "/posts/default");
Entry insert = myService.insert(postUrl, myEntry);
System.out.println(insert.getHtmlLink().getHref());