建立三个线程，A线程打印5次E，B线程打印5次D，C线程打印5次U，要求线程同时运行，交替打印5次EDU。

好的，下面是使用Python实现的代码：

import threading

class PrintThread(threading.Thread):
    def __init__(self, name, target_str):
        super().__init__(name=name)
        self.target_str = target_str

    def run(self):
        for _ in range(5):
            print(self.target_str, end="")
            print_lock.acquire()
            if self.name == "Thread A":
                b_cond.notify()
            elif self.name == "Thread B":
                c_cond.notify()
            elif self.name == "Thread C":
                a_cond.notify()
            print_lock.release()

print_lock = threading.Lock()
a_cond = threading.Condition()
b_cond = threading.Condition()
c_cond = threading.Condition()

a_thread = PrintThread("Thread A", "E")
b_thread = PrintThread("Thread B", "D")
c_thread = PrintThread("Thread C", "U")

a_thread.start()
b_thread.start()
c_thread.start()

print_lock.acquire()
b_cond.wait()
c_cond.wait()
print_lock.release()

for _ in range(4):
    print_lock.acquire()
    a_cond.wait()
    b_cond.wait()
    c_cond.wait()
    print_lock.release()

print_lock.acquire()
a_cond.wait()
b_cond.wait()
print_lock.release()

a_thread.join()
b_thread.join()
c_thread.join()

这里使用了`threading`模块创建了继承自`Thread`的`PrintThread`类，该类在`run`方法中打印指定的字符串，并使用`Lock`和`Condition`来控制线程的交替打印。具体地，`print_lock`用于控制打印的互斥，`a_cond`、`b_cond`、`c_cond`分别用于控制线程A、B、C的打印顺序。在`PrintThread`的`run`方法中，线程打印完字符后会先`acquire`锁，然后根据线程名字分别`notify`对应的`Condition`，最后再`release`锁。在主线程中，先等待线程B和线程C都打印完了第一次字符，然后循环交替等待线程A、B、C完成字符的打印，最后再等待线程A和线程B打印完最后一次字符后结束。