在写代码的时候，常常会遇到这样的情况：每次在执行一段代码的时候，都需要先执行一些代码；执行完之后，再执行另一些代码。比如在读写文件的时候，我们真正care的逻辑是"读写",至于文件流的初始化、打开、关闭、异常处理等都不是我们关心的。但是，每次在"读写"之前，我们需要执行打开操作，"读写"之后，需要执行关闭操作。这个时候就可以使用"execute around 模式"来提炼出"读写"前后的公共代码，从而把心思放在"读写"的逻辑上。
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代码：
/** * * Interface for specifying what to do with the file resource. * */ public interface FileWriterAction { void writeFile(FileWriter writer) throws IOException; } /** * * SimpleFileWriter handles opening and closing file for the user. The user only has to specify what * to do with the file resource through {@link FileWriterAction} parameter. * */ public class SimpleFileWriter { /** * Constructor */ public SimpleFileWriter(String filename, FileWriterAction action) throws IOException { FileWriter writer = new FileWriter(filename); // 读写前的操作 try { action.writeFile(writer); // 读写 } finally { writer.close(); // 读写后的操作 } } } /** * The Execute Around idiom specifies some code to be executed before and after a method. Typically * the idiom is used when the API has methods to be executed in pairs, such as resource * allocation/deallocation or lock acquisition/release. * <p> * In this example, we have {@link SimpleFileWriter} class that opens and closes the file for the * user. The user specifies only what to do with the file by providing the {@link FileWriterAction} * implementation. * */ public class App { /** * Program entry point */ public static void main(String[] args) throws IOException { new SimpleFileWriter("testfile.txt", new FileWriterAction() { @Override public void writeFile(FileWriter writer) throws IOException { // 真正关心的"读写"逻辑 writer.write("Hello"); writer.append(" "); writer.append("there!"); } }); } }