小编use*_*811的帖子

学习Python并且有点卡住了.

我正在尝试将变量设置为相等,int(stringToInt)或者如果字符串为空则设置为None.

我试着这样做variable = int(stringToInt) or None但是如果字符串为空则会出错而不是仅将其设置为None.

你知道这个吗？

我正在尝试使用XStream反序列化此XML文件,我收到此错误

Exception in thread "main" com.thoughtworks.xstream.converters.ConversionException: Authors : Authors
---- Debugging information ----
message             : Authors
cause-exception     : com.thoughtworks.xstream.mapper.CannotResolveClassException
cause-message       : Authors
class               : java.util.ArrayList
required-type       : java.util.ArrayList
converter-type      : com.thoughtworks.xstream.converters.collections.CollectionConverter
path                : /ListOfDBook/DBook/Authors
class[1]            : com.test.books.ListOfDBook
converter-type[1]   : com.thoughtworks.xstream.converters.reflection.ReflectionConverter
version             : null
-------------------------------
    at com.thoughtworks.xstream.core.TreeUnmarshaller.convert(TreeUnmarshaller.java:79)
    at com.thoughtworks.xstream.core.AbstractReferenceUnmarshaller.convert(AbstractReferenceUnmarshaller.java:65)
    at com.thoughtworks.xstream.core.TreeUnmarshaller.convertAnother(TreeUnmarshaller.java:66)
    at com.thoughtworks.xstream.converters.reflection.AbstractReflectionConverter.unmarshallField(AbstractReflectionConverter.java:355)
    at com.thoughtworks.xstream.converters.reflection.AbstractReflectionConverter.doUnmarshal(AbstractReflectionConverter.java:306)
    at com.thoughtworks.xstream.converters.reflection.AbstractReflectionConverter.unmarshal(AbstractReflectionConverter.java:234)
    at com.thoughtworks.xstream.core.TreeUnmarshaller.convert(TreeUnmarshaller.java:72)
    at com.thoughtworks.xstream.core.AbstractReferenceUnmarshaller.convert(AbstractReferenceUnmarshaller.java:65)
    at com.thoughtworks.xstream.core.TreeUnmarshaller.convertAnother(TreeUnmarshaller.java:66)
    at com.thoughtworks.xstream.core.TreeUnmarshaller.convertAnother(TreeUnmarshaller.java:50)
    at com.thoughtworks.xstream.core.TreeUnmarshaller.start(TreeUnmarshaller.java:134)
    at com.thoughtworks.xstream.core.AbstractTreeMarshallingStrategy.unmarshal(AbstractTreeMarshallingStrategy.java:32)
    at com.thoughtworks.xstream.XStream.unmarshal(XStream.java:1058)
    at com.thoughtworks.xstream.XStream.unmarshal(XStream.java:1042)
    at com.thoughtworks.xstream.XStream.fromXML(XStream.java:922)
    at com.test.booktest.BookImport.getBooks(BookImport.java:34)
    at com.test.booktest.Client.main(Client.java:6)
Caused by: …

我想知道这些同步方式之间的区别是什么

List<Integer> intList = Collections.synchronizedList(new ArrayList<Integer>());

synchronized (intList) {
    //Stuff
}

并使用对象锁

Object objectLock = new Object();

List<Integer> intList = new ArrayList<Integer>();

synchronized (objectLock) {
    //Stuff
}

我有一本书清单

List<Book> books = new ArrayList<Book>();

public class Book {
    String name;
    List<Author> authors;
}

本书包含作者列表,其中包含ID,姓名和年龄

public class Author {
    int ID;
    String Name;
    int Age;
}

我可以遍历书籍列表并返回BookName = x的位置,但我不知道如何搜索Author并返回Name = y的位置.

我有格式的数据

List<Object[]> data = new ArrayList<Object[]>();

for(Something s : SomeList) {
    Object[] tempList = { s.test, s.test2, s.test3 };

    data.add(tempList);
}

所以我有一个ArrayList的Objects[].现在我想把ArrayList对象变成一个Object[][]所以我有格式的数据

Object[][] data = { { test, test2, test3 }, { test4, test5, test6 } };

但我不知道该怎么做.

这个ArrayList步骤并不重要,它只是我试图弄清楚时所采取的方向.如果您有更好的方法来获取数据,Object[][]那就太好了.