Exceptions | Java OOP Knowledge Map

Exceptions

An exception is an object thrown when normal control flow is disrupted. Learn who throws, who catches, and which exceptions must be handled.Exception 是程序正常流程被打断时抛出的对象。你要知道什么时候 throw，谁 catch，以及 checked 和 unchecked 的区别。

throw / catch / finally

The direction exceptions travel异常的流动方向

try {
    readFile("data.txt");
} catch (IOException e) {
    System.out.println("File read failed");
} finally {
    closeResource();
}

throw: create and raise an exception.：创建并抛出异常。
catch: handle a specific exception type.：处理某种异常。
finally: run cleanup whether the operation succeeds or fails.：不管成功失败都执行，常用于释放资源。

Checked vs Unchecked

Whether the compiler forces handling编译器会不会逼你处理

Type类型	Example例子	Meaning怎么理解
Checked exception	`IOException`	External failures; the compiler requires catch or throws.外部环境导致的失败，编译器要求 catch 或 throws。
Unchecked exception	`NullPointerException`	Usually code bugs or invalid calls; not forced by the compiler.通常是代码 bug 或非法调用，不强制 catch。