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Data Types, Variables,
and Arrays
T
his chapter examines three of Java's most fundamental elements: data types, variables,
and arrays. As with all modern programming languages, Java supports several types
of data. You may use these types to declare variables and to create arrays. As you will
see, Java's approach to these items is clean, efficient, and cohesive.
Java Is a Strongly Typed Language
It is important to state at the outset that Java is a strongly typed language. Indeed, part of
Java's safety and robustness comes from this fact. Let's see what this means. First, every
variable has a type, every expression has a type, and every type is strictly defined. Second,
all assignments, whether explicit or via parameter passing in method calls, are checked for
type compatibility. There are no automatic coercions or conversions of conflicting types as
in some languages. The Java compiler checks all expressions and parameters to ensure that
the types are compatible. Any type mismatches are errors that must be corrected before the
compiler will finish compiling the class.
The Primitive Types
Java defines eight primitive types of data: byte, short, int, long, char, float, double, and boolean.
The primitive types are also commonly referred to as simple types, and both terms will be
used in this topic. These can be put in four groups:
Integers  This group includes byte, short, int, and long, which are for whole-valued
signed numbers.
Floating-point numbers  This group includes float and double, which represent
numbers with fractional precision.
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