JDK 5.0 的角落

1，dynamic cast

类似C++的dynamic_cast<T*>操作符，C#的as操作符，Java 5.0提供了安全的dynamic cast功能，不同的是它以类库的形式提供的：

Class.cast

public T cast(Object obj) Casts an object to the class or interface represented by this Class object. 　 Parameters: obj - the object to be cast Returns: the object after casting, or null if obj is null Throws: ClassCastException - if the object is not null and is not assignable to the type T. Since: 1.5

2，返回值协变

interface SomeInterface{
    Object get();
}

class CovariantImpl implements SomeInterface{
    public String get(){
        return "covariant";
    }
}

public class TestUntitled2 extends TestCase {
    public void testCovariant() {
        SomeInterface obj = new CovariantImpl();
        Assert.assertEquals("covariant", obj.get());
    }
}

3，类型安全的代理

类似只读代理Collections.unmodifiableXXX, 同步代理Collections.synchronizedXXX, Java 5.0提供了类型安全的代理：Collections.checkedXXX

4，Arrays.deepEquals()

5，毫无必要的static import

并且对同一个包内的static method不管用

package si;

class CovariantImpl
    public static void faint(){
    }
}

package si;

class SomeClass{
    public void test(){
        faint(); // compiler faints
    }
}

(to be continue...)

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