小编lam*_*988的帖子

我们可以用Java调用Windows cmd命令吗？例如,在Java程序中调用Windows的"解压缩"命令.这会很困难吗？

偶尔我会看到有人像这样创建一个arraylist,为什么？

List numbers = new ArrayList(  );

代替:

ArrayList<something> numbers = new ArrayList<something>();

我编写了一个servlet,但servlet还没有处于生产阶段.

我在servlet的Filter中添加了一个计数器,这样当并发请求数达到限制时,就不能再接受任何人了.我担心一些边缘情况,例如:假设系统已经达到49个并发请求(50个是最大值),并且在synchronized块中它使布尔变量"ok"为True,然后在下一个实例中,多个线程看到servlet是可用的,并急于进入并打破限制.

如果有任何缺陷,请帮助检查此代码:

public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain) throws IOException, ServletException {
        // TODO Auto-generated method stub
        // place your code here

        // pass the request along the filter chain
        conditionalInfoLog(logEnabled, "Incoming request...");
        conditionalInfoLog(logEnabled, "Number of concurrent request(s): " + count);
        boolean ok;
        synchronized (lock) {
            ok = count < limit;
            if(ok){
                count++;
            }
        }
        if (ok) {
            try{
                // let the request through and process as usual
                conditionalInfoLog(logEnabled, "Request accepted and processing, number of concurrent request(s): …

我是Java新手,具有Java背景,功能上的"自我"概念令我困惑.我理解第一个参数"self"意味着对象本身,但我不明白Python如何使这个工作.我也知道我可以使用"this"或"that"或"somethingElse",Python仍然会理解我的意思是使用该对象.

我从reddit 帖子中复制了一些代码:

class A():
    def __init__(self):
        self.value = ""

    def b(this):
        this.value = "b"

    def c(that):
        that.value = "c"

a = A()
print(a.value)

a.b()
print(a.value)
>>>"b"
a.c()
print(a.value)
>>>"c"

python如何知道我不是故意在第一个参数中使用对象？例如,我修改了上面的代码:

class A():
    def __init__(self):
        self.value = ""

    def b(this):
        this.value = "b"

    def c(that):
        that.value = "c"

    def somethingElse(someObjectIWantToPass):
        someObjectIWantToPass.value = "still referring A.value"

class B():
    def __init__(self):
        self.value = ""
a = A()
print(a.value)

a.b()
print(a.value)

a.c()
print(a.value)

a.somethingElse()

print(a.value)

b = B()

a.somethingElse(b)

print (b.value)

它打破了: …