Conditional Logic, Block Statements and Looping

Arithmetic Operators

Basic

Produce a result, no impact on values used.

1 + 2 = 3
5 - 4 = 1
4 * 2 = 8
13.0 / 5.0 = 2.6
13 / 5 - 2
13 % 5 = 3

Prefix & Postfix

Increase or decrease a value, replace original value.

int a = 5;
System.out.println(++a);  // 6, increase before being used in an expression
System.out.println(a);    // 6

int b = 5;
System.out.println(b++);  // 5
System.out.println(b);    // 6, increase after being used

Compound Assignment

Operate on a value, replace original value.

+= -= *= /= %=

Operator Precedence

Postfix (X++, X--) $\rightarrow$ Prefix (++X, --X) $\rightarrow$ Multiplicative (* / %) $\rightarrow$ Additive (+ -)

Logical Operators

	Operator	What resolves to true
AND	&	true & true
OR	|	false | true true | false true | true
XOR (exclusive or)	^	false ^ true true ^ false
NOT	!	false

Conditional Logical Operators

Similar to standard logical operators. Right side executes only when needed:

• && executes right only when left is true
• || executes right only when left is false

	Operator	What resolves to true
AND	&&	true && true
OR	||	false || true true || ----

Q: So what's so different?

A: When you use &, both sides are executed. With &&, right side is not always be executed. Consider below example:

// this could crash if denom == 0, cause divided by 0 is not allowed
if ( denom != 0 & numer / denom > 10 ) {
}
// so, you should do this
if ( denom != 0 && numer / denom > 10 ) {
}

Condition Logic

Relational Operators

> >= < <= == !=

Conditional Assignment

result = condition ? true-value : false-value;

If-else

if ( condition ) {
  statement;
}
else if ( condition ) {
  statement;
}
else {
  statement;
}

Block

Use { and } to create block.

Block and Variable Scope

Variable scope is limited to block.

Switch

Only primitive types supported (byte, short, int, long, char)

switch (value-to-test) {
  case matching-value-1:
    statements
    break;
  .
  .
  .
  case matching-value-N:
    statements
    break;
  default:
    statements
}

Looping

While

while ( condition ) {
  statement;
}

Do-while

do {
  statment;
} while ( condition );

For

for (initialize; condition; update) {
  statement;
}

For-each

for ( loop-variable : array ) {
  statement;
}