How do memory management techniques in Java functions work with the garbage collector?

In Java, memory management technology cooperates with the garbage collector to manage memory: stack allocation: basic data types and references are stored on the stack and managed by the virtual machine. Heap allocation: Objects are stored on the heap, allocated using the new operator, and managed by the garbage collector. Garbage Collector: A mark-and-sweep or generational garbage collector automatically detects and reclaims unreferenced objects. Weak and phantom references: Used to manage short-lived objects or simply track the existence of an object. Practical case: empty the variable to release the reference to the object on the heap so that the garbage collector can recycle the object.

How memory management technology in Java functions works with the garbage collector

In Java, memory management is usually through garbage The collector does this automatically. However, understanding how memory management techniques work with the garbage collector is critical to optimizing the performance of your Java applications.

Memory management technology

• Stack allocation: Basic data types and references are stored on the stack and are managed by the virtual machine. When a function is called, parameters and local variables are allocated space on the stack. These variables will be cleared when the function returns.
• Heap allocation: Objects are stored on the heap and require manual management. When creating a new object, the new operator allocates memory on the heap. Objects can be held by multiple references. When an object is no longer referenced, it will be reclaimed by the garbage collector.

Garbage Collector

The garbage collector is an automatic memory management mechanism that detects and reclaims objects that are no longer referenced by the program. There are two main types of garbage collectors in Java:

• Mark-and-sweep garbage collector: Marks all reachable objects and then clears unmarked objects.
• Generational garbage collector: Divides objects into different generations with different life cycles and uses different collection strategies for each generation.

Cooperation of memory management technology and garbage collector

Memory management technology works closely with garbage collector to improve the memory utilization and performance of the program.

• Stack allocation: Variables on the stack have nothing to do with the garbage collector because they are automatically released when the function returns.
• Heap allocation: The garbage collector is responsible for releasing objects on the heap that are no longer referenced.
• Weak reference: Weak reference can be used to deal with short-lived objects. When the object is no longer strongly referenced, it will be automatically recycled by the garbage collector.
• Virtual reference: Virtual reference is only used to track the object and does not prevent the garbage collector from recycling the object. This is useful for situations like cleaning up resources or cleaning up temporary state.

Practical Case

Consider the following Java code:

public class Example {
    static String str1;
    static String str2;

    public static void main(String[] args) {
        str1 = "Hello";
        str2 = str1;
        str1 = null;
    }
}

In this example:

• str1 and str2 are both allocated on the heap.
• When str1 = null, str1’s reference to the object will be cleared.
• str2 still holds a reference to the object. Therefore, the object will not be reclaimed by the garbage collector.
• Once str2 is also set to null, the object will be recycled by the garbage collector.

This example illustrates how to use a null value to clear a reference to an object so that it can be reclaimed by the garbage collector.

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