Understanding Variables, Constants, and Assignment Operators in Java, Slides of Java Programming

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Complex expressions

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Variables

To use variables two things must be done:

• Declaration
• Initialization See: Uninitialized.java (and Test.java) I am 68882420 inches tall. I am -1094369310 inches tall. C example: Variables are objects in your method (or class)

Variables

int x, y, z; x = 2; y = 3; z = 4; int x=2, y=3, z=4; Same as: Declaration Initialization Variables can be declared anywhere (preferably at start)

Assignment operator

= is the assignment operator The object to the right of the equals sign is stored into the object in the left int x, int y; y = 2; x = y+2;

Assignment operator

= is NOT a mathematic equals x=3; x=4; This does not mean 3=

Assignment operator

What does this code do? int x = 2; y = 3; y=x; x=y; What was the intention of this code?

Assignment operator

= is the assignment operator The object to the right of the equals sign is stored into the object in the left int x, int y; y = 2; x = y+2;

Increment operators

Two types of increment operators: x++; // increments after command vs ++x; // increments before command (see IncrementOperator.java)

Complex assignments

The following format is general for common operations: variable (operator)= expression variable = variable (operator) expression Examples: x+=2 x = x + 2 x*=y+2 x = x * (y + 2) (see AssignmentOperator.java)

Order of operations

Binary operators need two arguments Examples: (see BinaryOperators.java) 2+3, 5/2 and 6% Unary operators require only one argument: Examples: (see UnaryOperators.java) +x, x++, !x (! is the logical inversion operator for booleans)

Order of operations

When multiple operations have the same precedence level: Binary operations go from left to right Unary operations go right to left;