当我转换为maven项目时,错误是:
> An internal error occurred during: "Updating Maven Project".
> Unsupported IClasspathEntry kind=4
有什么问题？
java源代码如:
public class Test{
public static void main(String[] args){
System.out.println(X.Y.Z);
}
}
class X {
static class Y{
static String Z = "balck";
}
static C Y = new C();
}
class C{
String Z = "white";
}
为什么结果是:white？
我找到了/django/core/paginator.py 源代码：
class Paginator(object):
def __init__(self, object_list, per_page, orphans=0, allow_empty_first_page=True):
self.object_list = object_list
self.per_page = int(per_page)
self.orphans = int(orphans)
self.allow_empty_first_page = allow_empty_first_page
self._num_pages = self._count = None
孤儿属性是什么意思？
public class Foo {
private static Foo foo;
private Foo(){}
public static Foo getInstance(){
if (foo==null){
try {
Thread.sleep(1);
} catch (InterruptedException e) {}
foo = new Foo();
System.out.println(foo+"----"+Thread.currentThread().getName());
}
return foo;
}
public static void main(String[] args) throws Exception {
Thread thread1 = new Thread(new Runnable() {
@Override
public void run() {
Foo foo1 = Foo.getInstance();
}
},"thread1");
Thread thread2 = new Thread(new Runnable() {
@Override
public void run() {
Foo foo2 = Foo.getInstance();
}
},"thread2");
thread1.start();
thread2.start();
} …在dataframe中，如何合并两行，例如148将merge合并142为新行并删除两行。
title collectionsCount subscribersCount entriesCount viewsCount
148 Android 697977 100213 6803 10610138
142 Java 103821 65303 1493 1590201
161 iOS 163137 65896 3601 3739843
177 JavaScript 222100 88872 2412 3548736
16 Python 45234 45100 1007 930588
162 Swift 28498 30317 1180 928488
20 PHP 15376 25143 375 329720
62 Go 5321 12881 179 145851
41 C++ 3495 18404 101 75019
17 C 2213 14870 50 52019
63 Ruby 1543 6711 40 45162