Suppose you are given the following code:<\/p>\n
\r\nclass FooBar {\r\n public void foo() {\r\n for (int i = 0; i < n; i++) {\r\n print(\"foo\");\r\n }\r\n }\r\n\r\n public void bar() {\r\n for (int i = 0; i < n; i++) {\r\n print(\"bar\");\r\n }\r\n }\r\n}\r\n<\/pre>\nThe same instance of FooBar will be passed to two different threads:<\/p>\n
Modify the given program to output \"foobar\" n times.<\/p>\n
Example 1<\/strong>: Example 2<\/strong>: [Problem Link<\/a>]<\/p>\n Why use Semaphore<\/a> and not ReentrantLock<\/a>?<\/p>\n A semaphore initialized to one, and which is used such that it only has at most one permit available, can serve as a mutual exclusion lock. This is more commonly known as a binary semaphore, because it only has two states: one permit available, or zero permits available. When used in this way, the binary semaphore has the property (unlike many Lock implementations), that the \"lock\" can be released by a thread other than the owner (as semaphores have no notion of ownership). This can be useful in some specialized contexts, such as deadlock recovery<\/strong><\/em>.<\/p>\n Suppose you are given the following code: class FooBar { public void foo() { for (int i = 0; i < n; i++) { print(\"foo\"); } } public void bar() { for (int i = 0; i < n; i++) { print(\"bar\"); } } } The same instance of FooBar will be passed to two […]\n<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[1],"tags":[],"class_list":["post-11398","post","type-post","status-publish","format-standard","hentry","category-uncategorized"],"_links":{"self":[{"href":"https:\/\/www.softwareeverydayblog.com\/index.php?rest_route=\/wp\/v2\/posts\/11398","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.softwareeverydayblog.com\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.softwareeverydayblog.com\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.softwareeverydayblog.com\/index.php?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/www.softwareeverydayblog.com\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=11398"}],"version-history":[{"count":5,"href":"https:\/\/www.softwareeverydayblog.com\/index.php?rest_route=\/wp\/v2\/posts\/11398\/revisions"}],"predecessor-version":[{"id":11400,"href":"https:\/\/www.softwareeverydayblog.com\/index.php?rest_route=\/wp\/v2\/posts\/11398\/revisions\/11400"}],"wp:attachment":[{"href":"https:\/\/www.softwareeverydayblog.com\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=11398"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.softwareeverydayblog.com\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=11398"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.softwareeverydayblog.com\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=11398"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}
\nInput: n = 1
\nOutput: \"foobar\"
\nExplanation: There are two threads being fired asynchronously. One of them calls foo(), while the other calls bar().
\n\"foobar\" is being output 1 time.<\/p>\n
\nInput: n = 2
\nOutput: \"foobarfoobar\"
\nExplanation: \"foobar\" is being output 2 times.<\/p>\n\r\nclass FooBar {\r\n private int n;\r\n private final Semaphore mutexFoo = new Semaphore(1);\r\n private final Semaphore mutexBar = new Semaphore(1);\r\n\r\n public FooBar(int n) {\r\n this.n = n;\r\n try {\r\n mutexBar.acquire();\r\n } catch ( Exception e ) {}\r\n }\r\n\r\n public void foo(Runnable printFoo) throws InterruptedException {\r\n \r\n for (int i = 0; i < n; i++) {\r\n \r\n \/\/ printFoo.run() outputs \"foo\". Do not change or remove this line.\r\n mutexFoo.acquire();\r\n printFoo.run();\r\n mutexBar.release();\r\n }\r\n }\r\n\r\n public void bar(Runnable printBar) throws InterruptedException {\r\n \r\n for (int i = 0; i < n; i++) { \r\n \/\/ printBar.run() outputs \"bar\". Do not change or remove this line.\r\n mutexBar.acquire();\r\n printBar.run();\r\n mutexFoo.release();\r\n }\r\n }\r\n}\r\n<\/pre>\n","protected":false},"excerpt":{"rendered":"