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<b>Trail:</b> Learning the Java Language

<br /><b>Lesson:</b> Language Basics

<br /><b>Section:</b> Operators

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<div class="linkLESSON"><a href="index.html">Language Basics</a></div>

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<div class="linkBHEAD"><a href="arrays.html">Arrays</a></div>

<div class="linkBHEAD"><a href="variablesummary.html">Summary of Variables</a></div>

<div class="linkQUESTIONS"><a href="QandE/questions_variables.html">Questions and Exercises</a></div>

<div class="linkAHEAD"><a href="operators.html">Operators</a></div>

<div class="nolinkBHEAD">Assignment, Arithmetic, and Unary Operators</div>

<div class="linkBHEAD"><a href="op2.html">Equality, Relational, and Conditional Operators </a></div>

<div class="linkBHEAD"><a href="op3.html">Bitwise and Bit Shift Operators</a></div>

<div class="linkBHEAD"><a href="opsummary.html">Summary of Operators</a></div>

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<a href="../index.html" target="_top">Learning the Java Language</a>

<a href="index.html" target="_top">Language Basics</a>

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<div id="PageTitle"><h1>Assignment, Arithmetic, and Unary Operators</h1></div>

<h2>The Simple Assignment Operator</h2>

<p>One of the most common operators that you'll encounter is the simple assignment operator "<code>=</code>". You saw this operator in the Bicycle class; it assigns the value on its right to the operand on its left:</p>

int cadence = 0;

int speed = 0;

int gear = 1;

</pre></div>

<p>This operator can also be used on objects to assign <i>object references</i>, as discussed in

<a class="TutorialLink" target="_top" href="../javaOO/objectcreation.html">Creating Objects</a>.</p>

<h2>The Arithmetic Operators</h2>

<p>The Java programming language provides operators that perform addition, subtraction, multiplication, and division. There's a good chance you'll recognize them by their counterparts in basic mathematics. The only symbol that might look new to you is "<code>%</code>", which divides one operand by another and returns the remainder as its result.</p>

+ additive operator (also used for

String concatenation)

- subtraction operator

* multiplication operator

/ division operator

% remainder operator

</pre></div>

<p>The following program,

<a class="SourceLink" target="_blank" href="examples/ArithmeticDemo.java" onclick="showCode('../../displayCode.html', 'examples/ArithmeticDemo.java'); return false;"><code>ArithmeticDemo</code></a>, tests the arithmetic operators.</p>

class ArithmeticDemo {

public static void main (String[] args){

// result is now 3

int result = 1 + 2;

System.out.println(result);

// result is now 2

result = result - 1;

System.out.println(result);

// result is now 4

result = result * 2;

System.out.println(result);

// result is now 2

result = result / 2;

System.out.println(result);

// result is now 10

result = result + 8;

// result is now 3

result = result % 7;

System.out.println(result);

}

</pre></div>

<p>You can also combine the arithmetic operators with the simple assignment operator to create <i>compound assignments</i>. For example, <code>x+=1;</code> and <code>x=x+1;</code> both increment the value of <code>x</code> by 1.</p>

<p>The <code>+</code> operator can also be used for concatenating (joining) two strings together, as shown in the following

<a class="SourceLink" target="_blank" href="examples/ConcatDemo.java" onclick="showCode('../../displayCode.html', 'examples/ConcatDemo.java'); return false;"><code>ConcatDemo</code></a> program:</p>

class ConcatDemo {

public static void main(String[] args){

String firstString = "This is";

String secondString =

" a concatenated string.";

String thirdString =

firstString+secondString;

System.out.println(thirdString);

}

</pre></div>

<p>By the end of this program, the variable <code>thirdString</code> contains "This is a concatenated string.", which gets printed to standard output.</p>

<h2>The Unary Operators</h2>

<p>The unary operators require only one operand; they perform various operations such as incrementing/decrementing a value by one, negating an expression, or inverting the value of a boolean.</p>

+ Unary plus operator; indicates

positive value (numbers are

positive without this, however)

- Unary minus operator; negates

an expression

++ Increment operator; increments

a value by 1

-- Decrement operator; decrements

a value by 1

! Logical complement operator;

inverts the value of a boolean

</pre></div>

<p>The following program,

<a class="SourceLink" target="_blank" href="examples/UnaryDemo.java" onclick="showCode('../../displayCode.html', 'examples/UnaryDemo.java'); return false;"><code>UnaryDemo</code></a>, tests the unary operators:</p>

class UnaryDemo {

public static void main(String[] args){

// result is now 1

int result = +1;

System.out.println(result);

// result is now 0

result--;

System.out.println(result);

// result is now 1

result++;

System.out.println(result);

// result is now -1

result = -result;

System.out.println(result);

boolean success = false;

// false

System.out.println(success);

// true

System.out.println(!success);

}

</pre></div>

<p>The increment/decrement operators can be applied before (prefix) or after (postfix) the operand. The code <code>result++;</code> and <code>++result;</code> will both end in <code>result</code> being incremented by one. The only difference is that the prefix version (<code>++result</code>) evaluates to the incremented value, whereas the postfix version (<code>result++</code>) evaluates to the original value. If you are just performing a simple increment/decrement, it doesn't really matter which version you choose. But if you use this operator in part of a larger expression, the one that you choose may make a significant difference.</p>

<p>The following program,

<a class="SourceLink" target="_blank" href="examples/PrePostDemo.java" onclick="showCode('../../displayCode.html', 'examples/PrePostDemo.java'); return false;"><code>PrePostDemo</code></a>, illustrates the prefix/postfix unary increment operator:</p>

class PrePostDemo {

public static void main(String[] args){

int i = 3;

i++;

// prints 4

System.out.println(i);

++i;

// prints 5

System.out.println(i);

// prints 6

System.out.println(++i);

// prints 6

System.out.println(i++);

// prints 7

System.out.println(i);

}

</pre></div>

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