The finalize method in java is a method provided in the Object class. Before the GC is ready to release the memory space occupied by the object, it will first call the finalize() method.
The finalize() method is a method provided in the Object class. Before the GC is ready to release the memory space occupied by the object, it will first call finalize() method. It is defined in Object as follows:
protected void finalize() throws Throwable { }1 The timing of finalize() call
is related to the destructor of C (object (The destructor will be called before clearing). In Java, due to the automatic recycling mechanism of GC, there is no guarantee that the finalize method will be executed in time (the timing of recycling garbage objects is uncertain), nor can they be guaranteed. will be executed (the program does not trigger garbage collection from beginning to end).
public class Finalizer {
@Override
protected void finalize() throws Throwable {
System.out.println("Finalizer-->finalize()");
}
public static void main(String[] args) {
Finalizer f = new Finalizer();
f = null;
}
}
//無輸出public class Finalizer {
@Override
protected void finalize() throws Throwable {
System.out.println("Finalizer-->finalize()");
}
public static void main(String[] args) {
Finalizer f = new Finalizer();
f = null;
System.gc();//手動(dòng)請(qǐng)求gc
}
}
//輸出 Finalizer-->finalize()2 When should it be used
The finalize() method is generally used to release non- Resources (such as open file resources, database connections, etc.), or memory allocated when calling non-Java methods (native methods) (such as the malloc() series functions of C language).
3 Why you should avoid using it
First of all, due to the uncertainty in the timing of calling the finalize() method, it changes from an object to The time it takes from the beginning of unreachability to the execution of the finalize() method is arbitrarily long. We cannot rely on the finalize() method to recycle the occupied resources in a timely manner. The possible situation is that the gc has not been triggered before we exhaust the resources. Therefore, the usual approach is to provide an explicit close() method for the client to manually transfer.
In addition, overriding the finalize() method means that more operations are required when recycling objects, thereby prolonging the time for object recycling.
4 Let the object live again
Using the feature that the finalize() method will only be called once at most, we can extend the life cycle of the object.
class User{
public static User user = null;
@Override
protected void finalize() throws Throwable {
System.out.println("User-->finalize()");
user = this;
}
}
public class FinalizerTest {
public static void main(String[] args) throws InterruptedException {
User user = new User();
user = null;
System.gc();
Thread.sleep(1000);
user = User.user;
System.out.println(user != null);//true
user = null;
System.gc();
Thread.sleep(1000);
System.out.println(user != null);//false
}
}Recommended tutorial: "java tutorial"
The above is the detailed content of What is the function of finalize method in java. For more information, please follow other related articles on the PHP Chinese website!
Hot AI Tools
Undress AI Tool
Undress images for free
Undresser.AI Undress
AI-powered app for creating realistic nude photos
AI Clothes Remover
Online AI tool for removing clothes from photos.
Clothoff.io
AI clothes remover
Video Face Swap
Swap faces in any video effortlessly with our completely free AI face swap tool!
Hot Article
Hot Tools
Notepad++7.3.1
Easy-to-use and free code editor
SublimeText3 Chinese version
Chinese version, very easy to use
Zend Studio 13.0.1
Powerful PHP integrated development environment
Dreamweaver CS6
Visual web development tools
SublimeText3 Mac version
God-level code editing software (SublimeText3)
VSCode settings.json location
Aug 01, 2025 am 06:12 AM
The settings.json file is located in the user-level or workspace-level path and is used to customize VSCode settings. 1. User-level path: Windows is C:\Users\\AppData\Roaming\Code\User\settings.json, macOS is /Users//Library/ApplicationSupport/Code/User/settings.json, Linux is /home//.config/Code/User/settings.json; 2. Workspace-level path: .vscode/settings in the project root directory
How to handle transactions in Java with JDBC?
Aug 02, 2025 pm 12:29 PM
To correctly handle JDBC transactions, you must first turn off the automatic commit mode, then perform multiple operations, and finally commit or rollback according to the results; 1. Call conn.setAutoCommit(false) to start the transaction; 2. Execute multiple SQL operations, such as INSERT and UPDATE; 3. Call conn.commit() if all operations are successful, and call conn.rollback() if an exception occurs to ensure data consistency; at the same time, try-with-resources should be used to manage resources, properly handle exceptions and close connections to avoid connection leakage; in addition, it is recommended to use connection pools and set save points to achieve partial rollback, and keep transactions as short as possible to improve performance.
Mastering Dependency Injection in Java with Spring and Guice
Aug 01, 2025 am 05:53 AM
DependencyInjection(DI)isadesignpatternwhereobjectsreceivedependenciesexternally,promotingloosecouplingandeasiertestingthroughconstructor,setter,orfieldinjection.2.SpringFrameworkusesannotationslike@Component,@Service,and@AutowiredwithJava-basedconfi
python itertools combinations example
Jul 31, 2025 am 09:53 AM
itertools.combinations is used to generate all non-repetitive combinations (order irrelevant) that selects a specified number of elements from the iterable object. Its usage includes: 1. Select 2 element combinations from the list, such as ('A','B'), ('A','C'), etc., to avoid repeated order; 2. Take 3 character combinations of strings, such as "abc" and "abd", which are suitable for subsequence generation; 3. Find the combinations where the sum of two numbers is equal to the target value, such as 1 5=6, simplify the double loop logic; the difference between combinations and arrangement lies in whether the order is important, combinations regard AB and BA as the same, while permutations are regarded as different;
Troubleshooting Common Java `OutOfMemoryError` Scenarios
Jul 31, 2025 am 09:07 AM
java.lang.OutOfMemoryError: Javaheapspace indicates insufficient heap memory, and needs to check the processing of large objects, memory leaks and heap settings, and locate and optimize the code through the heap dump analysis tool; 2. Metaspace errors are common in dynamic class generation or hot deployment due to excessive class metadata, and MaxMetaspaceSize should be restricted and class loading should be optimized; 3. Unabletocreatenewnativethread due to exhausting system thread resources, it is necessary to check the number of threads, use thread pools, and adjust the stack size; 4. GCoverheadlimitexceeded means that GC is frequent but has less recycling, and GC logs should be analyzed and optimized.
python pytest fixture example
Jul 31, 2025 am 09:35 AM
fixture is a function used to provide preset environment or data for tests. 1. Use the @pytest.fixture decorator to define fixture; 2. Inject fixture in parameter form in the test function; 3. Execute setup before yield, and then teardown; 4. Control scope through scope parameters, such as function, module, etc.; 5. Place the shared fixture in conftest.py to achieve cross-file sharing, thereby improving the maintainability and reusability of tests.
Understanding the Java Virtual Machine (JVM) Internals
Aug 01, 2025 am 06:31 AM
TheJVMenablesJava’s"writeonce,runanywhere"capabilitybyexecutingbytecodethroughfourmaincomponents:1.TheClassLoaderSubsystemloads,links,andinitializes.classfilesusingbootstrap,extension,andapplicationclassloaders,ensuringsecureandlazyclassloa
How to work with Calendar in Java?
Aug 02, 2025 am 02:38 AM
Use classes in the java.time package to replace the old Date and Calendar classes; 2. Get the current date and time through LocalDate, LocalDateTime and LocalTime; 3. Create a specific date and time using the of() method; 4. Use the plus/minus method to immutably increase and decrease the time; 5. Use ZonedDateTime and ZoneId to process the time zone; 6. Format and parse date strings through DateTimeFormatter; 7. Use Instant to be compatible with the old date types when necessary; date processing in modern Java should give priority to using java.timeAPI, which provides clear, immutable and linear
