Java Reference
In-Depth Information
Summary of Key Concepts
The
print
and
println
methods represent two services provided by the
System.out
object.
■
An escape sequence can be used to represent a character that would other-
wise cause compilation problems.
■
A variable is a name for a memory location used to hold a value of a par-
ticular data type.
■
Accessing data leaves it intact in memory, but an assignment statement
overwrites the old data.
■
We cannot assign a value of one type to a variable of an incompatible type.
■
Constants hold a particular value for the duration of their existence.
■
Java has two kinds of numeric values: integer and floating point. There are
four integer data types and two floating point data types.
■
Java uses the 16-bit Unicode character set to represent character data.
■
Expressions are combinations of operators and operands used to perform
a calculation.
■
Java follows a well-defined set of precedence rules that governs the order
in which operators will be evaluated in an expression.
■
Narrowing conversions should be avoided because they can lose information.
■
The
Scanner
class provides methods for reading input of various types
from various sources.
■
Graphical data is represented by dividing it into many small pieces called pixels.
■
Java's coordinate system has the origin in the upper-left corner and all
visible coordinates are positive.
■
Colors are represented in Java using an RGB value—three values that
represent the contributions of the primary colors red, green, and blue.
■
The
Color
class contains several predefined colors that are commonly
used, and can be used to define many others.
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Applets are Java programs that are usually transported across a network
and executed using a Web browser.
■
Most shapes can be drawn filled (opaque) or unfilled (as an outline).
■
A bounding rectangle is used to define the position and size of curved
shapes such as ovals.
■
An arc is a segment of an oval beginning at a specific start angle and
extending for a distance specified by the arc angle.
■
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