instructions2.doc6.html

A Java virtual machine instruction consists of an opcode specifying the operation to be performed, f

<td><a name="87568"></a>
 

</Table><br></blockquote><p>
<a name="iadd.Forms"></a>
<p><b>Forms</b><br>
<blockquote><a name="68422"></a>
<i>iadd</i> = 96 (0x60)</blockquote><p>
<a name="iadd.Operand"></a>
<p><b>Operand Stack</b><br>
<blockquote><a name="68423"></a>
..., <i>value1</i><em>, </em><i>value2</i> <img src="chars/arrwdbrt.gif"> ..., <i>result</i></blockquote><p>
<a name="iadd.Description"></a>
<p><b>Description</b><br>
<blockquote><a name="68424"></a>
Both <i>value1</i> and <i>value2</i> must be of type <code>int</code>. The values are popped from the operand stack. The <code>int</code> <i>result</i> is <i>value1</i> + <i>value2</i>. The <i>result</i> is pushed onto the operand stack. </blockquote><p>
<blockquote><a name="68425"></a>
The result is the 32 low-order bits of the true mathematical result in a sufficiently wide two's-complement format, represented as a value of type <code>int</code>. If overflow occurs, then the sign of the result may not be the same as the sign of the mathematical sum of the two values.</blockquote><p>
<blockquote><a name="448552"></a>
Despite the fact that overflow may occur, execution of an <i>iadd</i> instruction never throws a runtime exception.</blockquote><p>

<a name="iaload"></a>
<hr><h2>iaload</h2>
<a name="iaload.Operation"></a>
<p><b>Operation</b><br>
<blockquote><a name="68438"></a>
Load <code>int</code> from array<p><Table Border="1">
</blockquote>

<p><b>Format</b><br>
<blockquote>

<tr><td><a name="68437"></a>
 <i>iaload</i>
<td><a name="87568"></a>
 

</Table><br></blockquote><p>
<a name="iaload.Forms"></a>
<p><b>Forms</b><br>
<blockquote><a name="68439"></a>
<i>iaload</i> = 46 (0x2e)</blockquote><p>
<a name="iaload.Operand"></a>
<p><b>Operand Stack</b><br>
<blockquote><a name="68440"></a>
..., <i>arrayref</i>, <i>index</i> <img src="chars/arrwdbrt.gif"> ..., <i>value</i></blockquote><p>
<a name="iaload.Description"></a>
<p><b>Description</b><br>
<blockquote><a name="68441"></a>
The <i>arrayref</i> must be of type <code>reference</code> and must refer to an array whose components are of type <code>int</code>. The <i>index</i> must be of type <code>int</code>. Both <i>arrayref</i> and <i>index</i> are popped from the operand stack. The <code>int</code> <i>value</i> in the component of the array at <i>index</i> is retrieved and pushed onto the operand stack.</blockquote><p>
<a name="iaload.Runtime"></a>
<p><b>Runtime Exceptions</b><br>
<blockquote><a name="68443"></a>
If <i>arrayref</i><em> </em>is <code>null</code>, <i>iaload</i> throws a <code>NullPointerException</code>. </blockquote><p>
<blockquote><a name="68444"></a>
Otherwise, if <i>index</i> is not within the bounds of the array referenced by <i>arrayref</i>, the <i>iaload</i> instruction throws an <code>ArrayIndexOutOfBoundsException</code>.</blockquote><p>

<a name="iand"></a>
<hr><h2>iand</h2>
<a name="iand.Operation"></a>
<p><b>Operation</b><br>
<blockquote><a name="68454"></a>
Boolean AND <code>int</code><p><Table Border="1">
</blockquote>

<p><b>Format</b><br>
<blockquote>

<tr><td><a name="68453"></a>
 <i>iand</i>
<td><a name="87568"></a>
 

</Table><br></blockquote><p>
<a name="iand.Forms"></a>
<p><b>Forms</b><br>
<blockquote><a name="68455"></a>
<i>iand</i> = 126 (0x7e)</blockquote><p>
<a name="iand.Operand"></a>
<p><b>Operand Stack</b><br>
<blockquote><a name="68456"></a>
..., <i>value1</i><em>, </em><i>value2</i> <img src="chars/arrwdbrt.gif"> ..., <i>result</i></blockquote><p>
<a name="iand.Description"></a>
<p><b>Description</b><br>
<blockquote><a name="68457"></a>
Both <i>value1</i> and <i>value2</i> must be of type <code>int</code>. They are popped from the operand stack. An <code>int</code> <i>result</i> is calculated by taking the bitwise AND (conjunction) of <i>value1</i> and <i>value2</i>. The <i>result</i> is pushed onto the operand stack.</blockquote><p>

<a name="iastore"></a>
<hr><h2>iastore</h2>
<a name="iastore.Operation"></a>
<p><b>Operation</b><br>
<blockquote><a name="68470"></a>
Store into <code>int</code> array<p><Table Border="1">
</blockquote>

<p><b>Format</b><br>
<blockquote>

<tr><td><a name="68469"></a>
 <i>iastore</i>
<td><a name="87568"></a>
 

</Table><br></blockquote><p>
<a name="iastore.Forms"></a>
<p><b>Forms</b><br>
<blockquote><a name="68471"></a>
<i>iastore</i> = 79 (0x4f)</blockquote><p>
<a name="iastore.Operand"></a>
<p><b>Operand Stack</b><br>
<blockquote><a name="68472"></a>
..., <i>arrayref</i>, <i>index</i>, <i>value</i> <img src="chars/arrwdbrt.gif"> ...</blockquote><p>
<a name="iastore.Description"></a>
<p><b>Description</b><br>
<blockquote><a name="68473"></a>
The <i>arrayref</i> must be of type <code>reference</code> and must refer to an array whose components are of type <code>int</code>. Both <i>index</i> and <i>value</i> must be of type <code>int</code>. The <i>arrayref</i>, <i>index</i>, and <i>value</i> are popped from the operand stack. The <code>int</code> <i>value</i> is stored as the component of the array indexed by <i>index</i>. </blockquote><p>
<a name="iastore.Runtime"></a>
<p><b>Runtime Exceptions</b><br>
<blockquote><a name="68475"></a>
If <i>arrayref</i><em> </em>is <code>null</code>, <i>iastore</i> throws a <code>NullPointerException</code>. </blockquote><p>
<blockquote><a name="68476"></a>
Otherwise, if <i>index</i> is not within the bounds of the array referenced by <i>arrayref</i>, the <i>iastore</i> instruction throws an <code>ArrayIndexOutOfBoundsException</code>.</blockquote><p>

<a name="iconst_i"></a>
<hr><h2>iconst_&lt;i&gt;</h2>
<a name="iconst_i.Operation"></a>
<p><b>Operation</b><br>
<blockquote><a name="68483"></a>
Push <code>int</code> constant<p><Table Border="1">
</blockquote>

<p><b>Format</b><br>
<blockquote>

<tr><td><a name="68482"></a>
 <i>iconst_&lt;i&gt;</i>
<td><a name="87568"></a>
 

</Table><br></blockquote><p>
<a name="iconst_i.Forms"></a>
<p><b>Forms</b><br>
<blockquote><a name="68484"></a>
<i>iconst_m1</i> = 2 (0x2) <i>iconst_0</i> = 3 (0x3) <i>iconst_1</i> = 4 (0x4) <i>iconst_2</i> = 5 (0x5) <i>iconst_3</i> = 6 (0x6) <i>iconst_4</i> = 7 (0x7) <i>iconst_5</i> = 8 (0x8)</blockquote><p>
<a name="iconst_i.Operand"></a>
<p><b>Operand Stack</b><br>
<blockquote><a name="68485"></a>
... <img src="chars/arrwdbrt.gif"> ..., <i>&lt;i&gt;</i></blockquote><p>
<a name="iconst_i.Description"></a>
<p><b>Description</b><br>
<blockquote><a name="68486"></a>
Push the <code>int</code> constant <i>&lt;i&gt;</i> (-<i>1</i>, <i>0</i>, <i>1</i>, <i>2</i>, <i>3</i>, <i>4</i> or <i>5</i>) onto the operand stack. </blockquote><p>
<a name="iconst_i.Notes"></a>
<p><b>Notes</b><br>
<blockquote><a name="68487"></a>
Each of this family of instructions is equivalent to <i>bipush</i> <i>&lt;i&gt;</i> for the respective value of <i>&lt;i&gt;</i>, except that the operand <i>&lt;i&gt;</i> is implicit.</blockquote><p>

<a name="idiv"></a>
<hr><h2>idiv</h2>
<a name="idiv.Operation"></a>
<p><b>Operation</b><br>
<blockquote><a name="68497"></a>
Divide <code>int</code><p><Table Border="1">
</blockquote>

<p><b>Format</b><br>
<blockquote>

<tr><td><a name="68496"></a>
 <i>idiv</i>
<td><a name="87568"></a>
 

</Table><br></blockquote><p>
<a name="idiv.Forms"></a>
<p><b>Forms</b><br>
<blockquote><a name="68498"></a>
<i>idiv</i> = 108 (0x6c)</blockquote><p>
<a name="idiv.Operand"></a>
<p><b>Operand Stack</b><br>
<blockquote><a name="68499"></a>
..., <i>value1</i><em>, </em><i>value2</i> <img src="chars/arrwdbrt.gif"> ..., <i>result</i></blockquote><p>
<a name="idiv.Description"></a>
<p><b>Description</b><br>
<blockquote><a name="68500"></a>
Both <i>value1</i> and <i>value2</i> must be of type <code>int</code>. The values are popped from the operand stack. The <code>int</code> <i>result</i> is the value of the Java programming language expression <i>value1</i> / <i>value2</i>. The <i>result</i> is pushed onto the operand stack.</blockquote><p>
<blockquote><a name="68501"></a>
An <code>int</code> division rounds towards 0; that is, the quotient produced for <code>int</code> values in <i>n</i>/<i>d</i> is an <code>int</code> value <i>q</i> whose magnitude is as large as possible while satisfying <img src="Instructions2.doc.anc6.gif">. Moreover, <i>q </i>is positive when <img src="Instructions2.doc.anc7.gif">  and <i>n</i> and <i>d</i> have the same sign, but <i>q</i> is negative when <img src="Instructions2.doc.anc8.gif">
and <i>n</i> and <i>d </i>have opposite signs. </blockquote><p>
<blockquote><a name="68511"></a>
There is one special case that does not satisfy this rule: if the dividend is the negative integer of largest possible magnitude for the <code>int</code> type, and the divisor is -<i>1</i>, then overflow occurs, and the result is equal to the dividend. Despite the overflow, no exception is thrown in this case. </blockquote><p>
<a name="idiv.Runtime"></a>
<p><b>Runtime Exception</b><br>
<blockquote><a name="68513"></a>
If the value of the divisor in an <code>int</code> division is 0, <i>idiv</i> throws an <code>ArithmeticException</code>.</blockquote><p>

<a name="if_acmpcond"></a>
<hr><h2>if_acmp&lt;cond&gt;</h2>
<a name="if_acmpcond.Operation"></a>
<p><b>Operation</b><br>
<blockquote><a name="339213"></a>
&#32;Branch if <code>reference</code> comparison succeeds<p><Table Border="1">
</blockquote>

<p><b>Format</b><br>
<blockquote>

<tr><td><a name="339202"></a>
 <i>if_acmp&lt;cond&gt;</i>
<td><a name="339204"></a>
 

<tr><td><a name="339206"></a>
 <i>branchbyte1</i>
<td><a name="339208"></a>
 

<tr><td><a name="339210"></a>
 <i>branchbyte2</i>
<td><a name="339212"></a>
 

</Table><br></blockquote><p>
<a name="if_acmpcond.Forms"></a>
<p><b>Forms</b><br>
<blockquote><a name="68525"></a>
<i>if_acmpeq</i> = 165 (0xa5) <i>if_acmpne</i> = 166 (0xa6)</blockquote><p>
<a name="if_acmpcond.Operand"></a>
<p><b>Operand Stack</b><br>
<blockquote><a name="68526"></a>
..., <i>value1</i>, <i>value2</i> <img src="chars/arrwdbrt.gif"> ...</blockquote><p>
<a name="if_acmpcond.Description"></a>
<p><b>Description</b><br>
<blockquote><a name="68527"></a>
Both <i>value1</i> and <i>value2</i> must be of type <code>reference</code>. They are both popped from the operand stack and compared. The results of the comparison are as follows:</blockquote><p>
<ul><li><i>eq</i> 	succeeds if and only if <i>value1</i> = <i>value2</i>
<li><i>ne</i> 	succeeds if and only if <i>value1</i> <img src="chars/notequal.gif"> <i>value2</i>
</ul><blockquote><a name="68530"></a>
If <em>the comparison succeeds, the unsigned </em><i>branchbyte1</i> and <i>branchbyte2</i> are used to construct a signed 16-bit offset, where the offset is calculated to be (<i>branchbyte1</i> << 8) | <i>branchbyte2</i>. Execution then proceeds at that offset from the address of the opcode of this <i>if_acmp&lt;cond&gt;</i> instruction. The target address must be that of an opcode of an instruction within the method that contains this <i>if_acmp&lt;cond&gt;</i> instruction.</blockquote><p>
<blockquote><a name="68531"></a>
Otherwise, if the comparison fails, execution proceeds at the address of the instruction following this <i>if_acmp&lt;cond&gt;</i> instruction.</blockquote><p>

<a name="if_icmpcond"></a>
<hr><h2>if_icmp&lt;cond&gt;</h2>
<a name="if_icmpcond.Operation"></a>
<p><b>Operation</b><br>
<blockquote><a name="68548"></a>