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Every Java virtual machine implementation must have a bootstrap class loader that is capable of loading trusted classes, as well as an extension class loader or application class loader. The Java virtual machine specification does not specify how a class loader should locate classes.
===Virtual
The JVM operates on specific types of data as specified in Java Virtual Machine specifications. The data types can be divided<ref>{{Cite web|url=https://docs.oracle.com/javase/specs/jvms/se8/html/jvms-2.html#jvms-2.2|title=Chapter 2. The Structure of the Java Virtual Machine|access-date=2021-09-15|archive-date=2021-09-15|archive-url=https://web.archive.org/web/20210915050448/https://docs.oracle.com/javase/specs/jvms/se8/html/jvms-2.html#jvms-2.2|url-status=live}}</ref> into primitive types ([[integer]]s, Floating-point, long etc.) and Reference types. The earlier JVM were only [[32-bit computing|32-bit]] machines. <code>long</code> and <code>double</code> types, which are [[64-bit computing|64-bits]], are supported natively, but consume two units of storage in a frame's local variables or operand stack, since each unit is 32 bits. <code>boolean</code>, <code>byte</code>, <code>short</code>, and <code>char</code> types are all [[sign-extended]] (except <code>char</code> which is [[Sign extension#zero-extended|zero-extended]]) and operated on as 32-bit integers, the same as <code>int</code> types. The smaller types only have a few type-specific instructions for loading, storing, and type conversion. <code>boolean</code> is operated on as 8-bit <code>byte</code> values, with 0 representing <code>false</code> and 1 representing <code>true</code>. (Although <code>boolean</code> has been treated as a type since ''The Java Virtual Machine Specification, Second Edition'' clarified this issue, in compiled and executed code there is little difference between a <code>boolean</code> and a <code>byte</code> except for [[Name mangling#Java|name mangling]] in [[method signature]]s and the type of boolean arrays. <code>boolean</code>s in method signatures are mangled as <code>Z</code> while <code>byte</code>s are mangled as <code>B</code>. Boolean arrays carry the type <code>boolean[]</code> but use 8 bits per element, and the JVM has no built-in capability to pack booleans into a [[bit array]], so except for the type they perform and behave the same as <code>byte</code> arrays. In all other uses, the <code>boolean</code> type is effectively unknown to the JVM as all instructions to operate on booleans are also used to operate on <code>byte</code>s.) However the newer JVM releases (OpenJDK HotSpot JVM) support 64-bit, so you can either have 32-bit/64-bit JVM on a 64-bit OS. The primary advantage of running Java in a 64-bit environment is the larger address space. This allows for a much larger Java heap size and an increased maximum number of Java Threads, which is needed for certain kinds of large applications; however there is a performance hit in using 64-bit JVM compared to 32-bit JVM.
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