Java意外类型做字符串比较，很奇怪

Question

This code is exactly as it is in the book Learning Java (Oracle Press Books), but it doesn't work. I don't understand why it doesn't work, it should work. I've tried it with both OpenJDK and Sun JDK 7, the error is the same.

ThreadCom.java:56: error: unexpected type
    if (thrd.getName().compareTo("Tick") = 0) {
                                ^
  required: variable
  found:    value
1 error

The code in question...

class MyThread implements Runnable {
    Thread thrd;
    TickTock ttOb;

    MyThread(String name, TickTock tt) {
            thrd = new Thread(this, name);
            ttOb = tt;
            thrd.start();
    }

    public void run() {
            if (thrd.getName().compareTo("Tick") = 0) { // <- that line
                    for (int i=0; i<5; i++) ttOb.tick(true);
                    ttOb.tick(false);
            } else {
                    for (int i=0; i<5; i++) ttOb.tock(true);
                    ttOb.tock(false);
            }
    }
}

The code is exactly as it is in the book.

Answer 1

this

thrd.getName().compareTo("Tick") = 0

should be

thrd.getName().compareTo("Tick") == 0

the first is an assignment. the second is a comparison.

Answer 2

I forgot the double equals, just noticed it.

if (thrd.getName().compareTo("Tick") = 0)

should be

if (thrd.getName().compareTo("Tick") == 0)