signalAll in Condition interface vs notifyAll in object
​​​http://stackoverflow.com/questions/10407708/signalall-in-condition-interface-vs-notifyall-in-object​​​
条件Condition中的signalALL 和 Object中的 notifyALL有啥区别？

Java中重写equals方法

public boolean equals(Objects x){
        if(this == x) return true;
        if(x == null) return false;
        if(this.getClass() != x.getClass()) return false;
        Date that = (Date) x;
        if(this.day != that.day) return false;

        return true;
    }