查看Effective Java，第2版第27页。 第7项:避免终结词

终结器是不可预测的，通常是危险的，而且通常是不必要的。永远不要在终结器中做任何时间紧迫的事情。从来没有 依赖终结器更新关键持久状态。

要终止一个资源，请使用try-finally:

// try-finally块保证终止方法的执行 Foo Foo =新的Foo(…); 尝试{ //用foo做必须做的事情 .．. }最后{ foo.terminate ();//显式终止方法 ｝

一般来说，最好不要依赖finalize()来做任何清理等。

根据Javadoc(值得一读)，它是:

当垃圾回收确定对象不再有引用时，由垃圾回收器在对象上调用。

正如Joachim指出的，如果对象总是可访问的，那么在程序的生命周期中，这可能永远不会发生。

此外，垃圾收集器不保证在任何特定时间运行。一般来说，我想说的是finalize()可能不是最好的方法，除非有特定的事情需要它。

查看Effective Java，第2版第27页。 第7项:避免终结词

终结器是不可预测的，通常是危险的，而且通常是不必要的。永远不要在终结器中做任何时间紧迫的事情。从来没有 依赖终结器更新关键持久状态。

要终止一个资源，请使用try-finally:

// try-finally块保证终止方法的执行 Foo Foo =新的Foo(…); 尝试{ //用foo做必须做的事情 .．. }最后{ foo.terminate ();//显式终止方法 ｝

Java allows objects to implement a method called finalize() that might get called. finalize() method gets called if the garbage collector tries to collect the object. If the garbage collector doesn't run, the method doesn't get called. If the garbage collector fails to collect the object and tries to run it again, the method doesn't get called in the second time. In practice, you are highly unlikely to use it in real projects. Just keep in mind that it might not get called and that it definitely won't be called twice. The finalize() method could run zero or one time. In the following code, finalize() method produces no output when we run it since the program exits before there is any need to run the garbage collector.

源

正如在https://wiki.sei.cmu.edu/confluence/display/java/MET12-J.+Do+not+use+finalizers上指出的那样，

There is no fixed time at which finalizers must be executed because time of execution depends on the Java Virtual Machine (JVM). The only guarantee is that any finalizer method that executes will do so sometime after the associated object has become unreachable (detected during the first cycle of garbage collection) and sometime before the garbage collector reclaims the associated object's storage (during the garbage collector's second cycle). Execution of an object's finalizer may be delayed for an arbitrarily long time after the object becomes unreachable. Consequently, invoking time-critical functionality such as closing file handles in an object's finalize() method is problematic.

Java finalize()方法不是析构函数，不应用于处理应用程序所依赖的逻辑。Java规范声明，不能保证在应用程序的生存期内调用finalize方法。

你可能想要的是一个finally和cleanup方法的组合，如:

MyClass myObj;

try {
    myObj = new MyClass();

    // ...
} finally {
    if (null != myObj) {
        myObj.cleanup();
    }
}

这将正确处理MyClass()构造函数抛出异常时的情况。