Heap Memory and Stack Memory in Java

The fact that Java is platform-independent is one of the main factors in its popularity. As long as the computer has a Java Runtime Environment (JRE) installed, Java programs can operate on a variety of different computer types. Most computer platforms, including Windows PCs, Macintosh computers, Unix or Linux systems, large mainframe computers, and mobile devices, can run a JRE. Some of the largest organizations in the world are constructed using the language because it has been around for such a long time. Java is widely used by banks, shops, insurance companies, utilities, and manufacturers.

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The core of Java is object-oriented. Because Java objects don’t reference any external data, the code is extremely robust. Although the language is thought to be fairly basic, it comes with a library of classes that provide frequently used utility methods that are essential to the operation of the majority of Java programs. The class library and Java API are integral components of the latter. The real difficulty in learning to use Java isn’t the language itself; rather, it’s the API. The Java API offers thousands of classes and tens of thousands of methods that you can utilize in your apps, but the language only has 50 keywords. Despite this, just a small percentage of the Java API is used by most developers, and they aren’t required to understand the entire API.

Memories Allocated by Java

The memory in Java is split into 5 distinct sections:

1.Class/Method

The memory block that houses the function Object() { [native code] }, method code, and variable code (static variables, runtime constants) for a Java application is known as the class method area. (In this context, “method” refers to the function written inside a class.) Every class’s class-level data is stored here, including the runtime constant pool, field and method data, and method code.

2. Heap

The memory block where objects are produced or stored is known as the Heap region. Memory is allocated for class interfaces and arrays in heap memory (an array is an object). It is utilized to run-time allocate memory to objects.

3. Stack

Each thread has a unique, concurrently constructed private JVM stack. To do dynamic linking and return method value, it is utilized to store data and partial results. Every time the method is called, a new frame is created and stored in the Java Stack. When a frame’s method call is finished, it is destroyed.

4. Program Counter Register

A program counter register is connected to each JVM thread that executes a certain method’s task. Unlike native methods, which have an indeterminate value for the program counter, non-native methods have a PC that contains the address of the next possible JVM instruction. A native pointer or the return address can be stored in a PC register depending on the platform.

5. Native Method Stacks

Native method stacks, often known as C stacks, are not created in Java. Each thread receives a specific amount of memory when it is formed, and it can be either fixed or dynamic.

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Heap Memory and Stack Memory in Java

To run an application as efficiently as possible, JVM divides memory into heap and stack memory. JVM designates memory to these actions from either Stack Memory or Heap Space whenever we declare new variables and objects, invoke new methods, define a String, or carry out similar operations. Let us look at Java Stack and Java Heap in detail.

• Stack Memory in Java

Java uses stack memory for both thread execution and allocation of static memory. It includes references to heap-based objects referred from a method as well as primitive variables that are particular to that method. This memory is accessed using the Last-In-First-Out (LIFO) method. A new block is formed on top of the stack each time we call a new method, and it contains values particular to that method, such as primitive variables and references to objects. After a method has finished running, its corresponding stack frame is flushed, control returns to the method that is called it, and the room is now open for the following method. Key features of stack memory are:

• As additional methods are called and returned, it expands and contracts.
• The stack’s internal variables only persist for the duration of the method that produced them.
• When the method has finished running, it is automatically allocated and deallocated.
• Java throws a java. lang.StackOverFlowError if this memory is full.
• In comparison to heap memory, access to this memory is quick.
• Because each thread has its stack, this memory is threadsafe.
• Heap Memory in Java

When Java objects and JRE classes are dynamically allocated memory at runtime, heap space is consumed. In heap space, new things are constantly produced, and stack memory stores the references to those new objects. We have access to these objects from wherever in the program since they have global access. This memory model can be divided into generations, which are smaller components and include:

1. Young Generation – All new objects are assigned and aged in this location. When this is full, there is a small garbage collection.
2. Old/Tenured Generation – Objects with a long shelf life are kept here. A threshold for the object’s age is specified when it is placed in the Young Generation, and once it is met, the object is transferred to the Old Generation.
3. Permanent Generation – this comprises JVM metadata for the application methods and runtime classes.

The key features of Java Heap are as follows:

• The Permanent Generation, Old or Tenured Generation, and Complex Memory Management Techniques are used to access it.
• Java issues the java. lang.OutOfMemoryError if the heap space is full.
• Compared to stack memory, access to this memory is slower.
• In contrast to stack, this memory is not automatically deallocated. A garbage Collector is required to release useless items to maintain the efficiency of memory consumption.
• A heap, unlike a stack, is not threadsafe and must be protected by carefully synchronizing the code.

Java’s Heap and Stack Memory Differences are:

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Conclusion

Java allocates memory using the heap and the stack. This article taught us how they operate and when to apply them to improve Java programs. Both are significant memory spaces from the Java point of view, but they serve different functions. The main distinction between heap memory and stack memory is that the heap memory keeps the objects and employs dynamic memory allocation and deallocation, whilst the stack memory is used to store the order of method execution and local variables.

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