Question

我正在尝试扩展“接口的交叉点”。所以：我所遵循的示例是尝试查找RandomAccessFile (Implemented Interfaces: Closeable, DataInput, DataOutput, AutoCloseable )和DataInputStream(Implemented Interfaces: Closeable, DataInput, AutoCloseable )的超接口，因此我们至少在Closeable和DataInput上有一个交集（当然我可以与AutoCloseable建立交集：所以代码就像这样：

private static <I extends DataInput & Closeable> Person read(I source) {
    try (I input = source) {
        return new Person(input.readLine(), Integer.valueOf(input.readLine()));         
    } catch (IOException e) {
        e.printStackTrace();
        return null;
    }
}

当我这样做时，效果很好：

public static void main(String[] args) throws IOException {  
    RandomAccessFile input = new RandomAccessFile("src\\main\\resorces\\person.txt", "rw");
    Person person2 = read(input);
    System.out.println(person2.toString());

}

但是当我这样做时：

public static void main(String[] args) throws IOException {     
    DataInputStream stream = new DataInputStream(new
        FileInputStream("src\\main\\resorces\\person.txt")); 
    Person person = read(stream); 
    System.out.println(person.toString());       

}

它让我感到厌恶：

Exception in thread "main" java.lang.NoSuchMethodError: `java.io.DataInput.close()V
at com.test.java8.l03.generics.Person.read(Person.java:34)
at com.test.java8.l03.generics.Person.main(Person.java:20)

以下是所有代码：

public class Person {

    public static void main(String[] args) throws IOException {

        /*DataInputStream stream = new DataInputStream(new FileInputStream("src\\main\\resorces\\person.txt"));
        Person person = read(stream);
        System.out.println(person.toString());*/


        RandomAccessFile input = new
          RandomAccessFile("src\\main\\resorces\\person.txt", "rw"); 
        Person person2 = read(input); System.out.println(person2.toString());
    }

    private static <I extends DataInput & Closeable> Person read(I source) {
        try (I input = source) {
            return new Person(input.readLine(), Integer.valueOf(input.readLine()));
        } catch (IOException e) {
            e.printStackTrace();
            return null;
        }

    }

    private static Person read(RandomAccessFile source) {
        try (RandomAccessFile input = source) {
            return new Person(input.readLine(), Integer.valueOf(input.readLine()));
        } catch (IOException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
            return null;
        }

    }

    private final String name;
    private final int age;

    public Person(String name, int age) {
        this.name = name;
        this.age = age;

    }
    public String getName() {
        return name;
    }

    public int getAge() {
        return age;
    }

    public String toString() {
        return "Person [name=" + name + ", age=" + age + "]";
    }
}

我不希望这个错误，因为交叉接口我扩展了Closeable。任何人都可以帮我这个吗？

但是不会抛出置换异常的接口：

private static <I extends Closeable & DataInput> Person read(I source) {
try (I input = source) {
    return new Person(input.readLine(), Integer.valueOf(input.readLine()));
} catch (IOException e) {
    e.printStackTrace();
    return null;
}

}

接口的交集是否可能不是等价关系（更准确地说，此操作数上的交集不是自反的）并且编译器将左侧接口作为返回值？

与此相关：DataInputStream实现DataInput并扩展实现Closeable的抽象类InputStream。 RandomAccessFile直接实现DataInput和Closeable，因此RandomAccessFile必须实现close（）方法而DataInputStream不实现（它可以使用实现Closeable接口的超类方法）？因此，使用动态方法调度时，编译器可能会混淆???

具有多个边界的有界类型参数RandomAccessFile＆amp; DataInputStream抛出java.lang.NoSuchMethodError：java.io.DataInput.close（）V

0 个答案: