References and libraries.
Java Collections Framework
Java Operators
Java Primitive & Wrapper Types
Arrays in Java
Functional Interfaces
Java Building Blocks
Recursion
java.lang.Math
java.lang.Number
java.lang.Byte
java.lang.Double
java.lang.Float
java.lang.Integer
java.lang.Long
java.lang.Short
java.math.BigDecimal
java.math.BigInteger
java.util.Collection
java.util.List
java.util.ArrayList
java.util.LinkedList
java.util.Set
java.util.HashSet
java.util.LinkedHashSet
java.util.random.RandomGenerator
java.util.random.RandomGenerator.JumpableGenerator
java.util.random.RandomGenerator.ArbitrarilyJumpableGenerator
java.util.random.RandomGenerator.LeapableGenerator
java.util.random.RandomGenerator.StreamableGenerator
java.util.random.RandomGenerator.SplittableGenerator
java.util.SplittableRandom
java.util.random.RandomGeneratorFactory
java.util.Random
java.security.SecureRandom
java.util.concurrent.ThreadLocalRandom
java.util.stream.BaseStream
java.util.stream.DoubleStream
java.util.stream.IntStream
java.util.stream.LongStream
java.util.stream.Stream
Apache Commons Math
Apache Commons RNG
Apache Commons Statistics
N. Bennett Introduction to Algorithms and Pseudocode
R. L. Graham, D. Knuth, O. Patashnik, Concrete Mathematics
D. Knuth, The Art of Computer Programming
T. Roughgarden, Algorithms Illuminated
Rosetta Code