Ngăn chặn các luồng truy nhập đồng thời các đối tượng dùng chung. Toàn bộ tiến trình này được quản lý bởi cơ chế đợi thông báo (wait-notify). Phương thức wait() báo cho dòng gọi từ bỏ monitor và nhập vào trạng thái ngủ cho đến khi các luồng khác sử dụng xong monitor và gọi phương thức notify(). | Learn HTML and CSS with w3schools Nested Elements Most HTML elements can be nested contain or be contained within other HTML elements . HTML documents consist of nested HTML elements. The following example contains three HTML elements. Notice that the p element is nested in the body element which in turn is nested in the html element. The results of these tags are shown in Figure . html body p This is my first paragraph p body html This is my first paragraph Figure The p element The p element is among the most common of elements. p This is my first paragraph p 8 The p element defines a new paragraph in the HTML document. 8 The element has a start tag p and an end tag p . 8 The element content is This is my first paragraph. The body element The body element defines the body of the HTML document. body p This is my first paragraph p body 14 Chapter 3 HTML Elements 8 The element has a start tag body and an end tag body . 8 The element content is another HTML element one or more paragraphs . There are usually dozens of elements within the body element. The html element The html element defines the entire HTML document. html body p This is my first paragraph p body html 8 The element has a start tag html and an end tag html . 8 The element content is another HTML element the body . Don t Forget the End Tag Most browsers will display HTML correctly even if you forget the end tag. p This is a paragraph p This is another paragraph The previous example will work in most browsers but don t rely on it. Forgetting the end tag can produce unexpected results or errors. NOTE Future versions of HTML will not allow you to skip end tags. 15 Learn HTML and CSS with w3schools Download from Wow eBook Empty HTML Elements HTML elements without content are called empty elements. Empty elements can be closed within the start tag. br is an empty element without a closing tag. It defines a line break. In XML and future versions of HTML all elements must be closed. .
