Immutable classes are Java classes whose objects can not be modified once created. Any modification in Immutable object result in new object. For example is String is immutable in Java. Mostly Immutable are also final in Java, in order to prevent sub class from overriding methods in Java which can compromise Immutability. You can achieve same functionality by making member as non final but private and not modifying them except in constructor.

Squirrels typically build leaf nests in the summer by weaving together small branches they've gnawed off of trees. These nests are lined with grass, moss, leaves and pine needles. Both male and female gray squirrels of all ages participate in building dens.
 

In all other pairs, first is a product made from the second.

By using
$_SERVER['HTTP_USER_AGENT']
variable.

Given that 50 paise and 25 paise coins are in the ratio of 7:3, they can be either 7 & 3 or 14 & 6.
As total 20 coins also includes Rs. 1 coins, so 50 paise & 25 paise coins are 7 & 3 respectively & Rs. 1 coins are 10.
Total amount = (100x10) + (50x7) + (25x3)=1425 paise or Rs.14.25.

A Jigsaw puzzle.