Alarm clock with "ringing" functionality
Calendar

You created an alarmclock, which is really just a time-representation. A Calendar has both a date and time component. I strongly, strongly suggest you use that so you can let your user define how he wants his date represented and let the API handle fancy stuff like timezones, summer hours, etc.

You can also look into the Java 8 time API but I think that might not be appropriate yet.

Enums

When you have a limited set of different possibilities, your mind should immediately wander to enums. This way you can represent your AM/PM by saying DayPart.AM and DayPart.PM instead of the literal string "AM" which could mistakenly be used as "aM", "am", "AX", etc. It will provide compile-time safety and is a lot more pleasant to work with.

Indentation

Stick to conventions. Some people indent a block with one tab (or 4 spaces), some with 2 spaces. This will keep the code readable for everyone.

Methods without a meaningful body

Look at your code here:

public int getHour() {
if ((hour &gt;= 1) &amp;&amp; (hour &lt;= 12)) {
}
return hour;
}


With formatting this becomes this:

public int getHour() {
    if ((hour &gt;= 1) &amp;&amp; (hour &lt;= 12)) {
    }

    return hour;
}


Can you tell what's wrong here? Note that there are several methods that have this construct!

Assignment vs Comparison

This is a very common mistake:

if (isAlarmRinging = true)


What you do here is set isAlarmRinging to true, you never compare it. 

Keep in mind:


Comparison: ==.
Assignment: =.


Unused parameters

In your method setTime you never use the parameter newMinute.
Likewise in method setAlarmTime you never use newAlarmAmOrPm.