Java异常基础

public class Test {public static void main(String[] args) {File f = new File("file.txt");FileInputStream input = new FileInputStream(f);}}

? ? 上面的代码编译器会报错，我们看下FileInputStream的源码，其中有：

public FileInputStream(File file) throws FileNotFoundException {String name = (file != null ? file.getPath() : null);SecurityManager security = System.getSecurityManager();if (security != null) {security.checkRead(name);}if (name == null) {throw new NullPointerException();}fd = new FileDescriptor();fd.incrementAndGetUseCount();open(name);}

? ? 可以看到FileInputStream的构造方法指出，它可能会抛出FileNotFoundException的异常。我们的编译器会检查，发现我们既没有声明异常，也没有抛出，这样就会报错。

public class Test {public static void main(String[] args) {File f = new File("file.txt");try {FileInputStream input = new FileInputStream(f);} catch (FileNotFoundException e) {e.printStackTrace();}}}

??