The super keyword is used in Java to refer to the parent class of the current object. Its main uses include accessing the parent class method, calling the parent class constructor, and resolving field name conflicts. 1. Access the parent class method: When the child class overrides the parent class method, the parent class version can be called through super.method() to extend its behavior rather than completely replace it; 2. Call the parent class constructor: Super() or super(args) is used in the child class constructor to initialize the parent class field, and the statement must be located on the first line of the child class constructor; 3. Resolve field name conflicts: If the child class defines the same name field as the parent class, super.fieldName can be used to explicitly access the parent class field.
The super keyword in Java is used to refer to the parent class (or superclass) of the current object. It's super handy when you're working with inheritance, especially if you want to access methods or constructors from the parent class that might be hidden or overridden in the subclass.
Let's break it down into common use cases so you can see how and why you'd use super .
Accessing Parent Class Methods
When a subclass overrides a method from its parent class, the version in the child class takes precedence. But sometimes you still want to run the parent's version — maybe to extend its behavior instead of completely replacing it.
For example:
class Animal {
void speak() {
System.out.println("Animal speaks");
}
}
class Dog extends Animal {
@Override
void speak() {
super.speak(); // calls the Animal version first
System.out.println("Dog barks");
}
}In this case:
-
super.speak()runs the original method fromAnimal - Then we add extra behavior specific to
Dog
This pattern is really useful when you want to build on existing logic without duplicating code.
Calling the Parent Class Constructor
If your subclass has a constructor, you often need to initialize fields that belong to the parent class. You can do that by calling the parent's constructor using super() as the first line in your subclass constructor.
Here's what that looks like:
class Vehicle {
Vehicle(String brand) {
System.out.println("Vehicle brand: " brand);
}
}
class Car extends Vehicle {
Car(String brand) {
super(brand); // must come first
System.out.println("Car created");
}
}A few things to note:
-
super()must be the first statement in the constructor - If you don't explicitly call
super(), Java adds a no-argsuper()for you automatically - If the parent doesn't have a no-arg constructor, you must provide the correct arguments
Resolving Field Name Conflicts
Sometimes a subclass defines a field with the same name as one in the parent class. In that case, you can use super.fieldName to access the parent's version.
Example:
class Parent {
int value = 10;
}
class Child extends Parent {
int value = 20;
void printValues() {
System.out.println("Child value: " value);
System.out.println("Parent value: " super.value);
}
}This helps avoid confusion when both classes define similar fields and you need to distinguish between them.
So yeah, super isn't magic — it's just a way to clearly say “I want to use something from my parent class.” Whether it's a method, constructor, or field, super gives you control over which version you're referring to.
And honestly, once you get used to it, it makes working with inheritance a lot cleaner and more flexible.
That's basically it. Not too complicated, but definitely important when you start building more complex class hierarchies.
The above is the detailed content of What is the super keyword 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)
Asynchronous Programming Techniques in Modern Java
Jul 07, 2025 am 02:24 AM
Java supports asynchronous programming including the use of CompletableFuture, responsive streams (such as ProjectReactor), and virtual threads in Java19. 1.CompletableFuture improves code readability and maintenance through chain calls, and supports task orchestration and exception handling; 2. ProjectReactor provides Mono and Flux types to implement responsive programming, with backpressure mechanism and rich operators; 3. Virtual threads reduce concurrency costs, are suitable for I/O-intensive tasks, and are lighter and easier to expand than traditional platform threads. Each method has applicable scenarios, and appropriate tools should be selected according to your needs and mixed models should be avoided to maintain simplicity
Best Practices for Using Enums in Java
Jul 07, 2025 am 02:35 AM
In Java, enums are suitable for representing fixed constant sets. Best practices include: 1. Use enum to represent fixed state or options to improve type safety and readability; 2. Add properties and methods to enums to enhance flexibility, such as defining fields, constructors, helper methods, etc.; 3. Use EnumMap and EnumSet to improve performance and type safety because they are more efficient based on arrays; 4. Avoid abuse of enums, such as dynamic values, frequent changes or complex logic scenarios, which should be replaced by other methods. Correct use of enum can improve code quality and reduce errors, but you need to pay attention to its applicable boundaries.
Understanding Java NIO and Its Advantages
Jul 08, 2025 am 02:55 AM
JavaNIO is a new IOAPI introduced by Java 1.4. 1) is aimed at buffers and channels, 2) contains Buffer, Channel and Selector core components, 3) supports non-blocking mode, and 4) handles concurrent connections more efficiently than traditional IO. Its advantages are reflected in: 1) Non-blocking IO reduces thread overhead, 2) Buffer improves data transmission efficiency, 3) Selector realizes multiplexing, and 4) Memory mapping speeds up file reading and writing. Note when using: 1) The flip/clear operation of the Buffer is easy to be confused, 2) Incomplete data needs to be processed manually without blocking, 3) Selector registration must be canceled in time, 4) NIO is not suitable for all scenarios.
How does a HashMap work internally in Java?
Jul 15, 2025 am 03:10 AM
HashMap implements key-value pair storage through hash tables in Java, and its core lies in quickly positioning data locations. 1. First use the hashCode() method of the key to generate a hash value and convert it into an array index through bit operations; 2. Different objects may generate the same hash value, resulting in conflicts. At this time, the node is mounted in the form of a linked list. After JDK8, the linked list is too long (default length 8) and it will be converted to a red and black tree to improve efficiency; 3. When using a custom class as a key, the equals() and hashCode() methods must be rewritten; 4. HashMap dynamically expands capacity. When the number of elements exceeds the capacity and multiplies by the load factor (default 0.75), expand and rehash; 5. HashMap is not thread-safe, and Concu should be used in multithreaded
Effective Use of Java Enums and Best Practices
Jul 07, 2025 am 02:43 AM
Java enumerations not only represent constants, but can also encapsulate behavior, carry data, and implement interfaces. 1. Enumeration is a class used to define fixed instances, such as week and state, which is safer than strings or integers; 2. It can carry data and methods, such as passing values ??through constructors and providing access methods; 3. It can use switch to handle different logics, with clear structure; 4. It can implement interfaces or abstract methods to make differentiated behaviors of different enumeration values; 5. Pay attention to avoid abuse, hard-code comparison, dependence on ordinal values, and reasonably naming and serialization.
What is a Singleton design pattern in Java?
Jul 09, 2025 am 01:32 AM
Singleton design pattern in Java ensures that a class has only one instance and provides a global access point through private constructors and static methods, which is suitable for controlling access to shared resources. Implementation methods include: 1. Lazy loading, that is, the instance is created only when the first request is requested, which is suitable for situations where resource consumption is high and not necessarily required; 2. Thread-safe processing, ensuring that only one instance is created in a multi-threaded environment through synchronization methods or double check locking, and reducing performance impact; 3. Hungry loading, which directly initializes the instance during class loading, is suitable for lightweight objects or scenarios that can be initialized in advance; 4. Enumeration implementation, using Java enumeration to naturally support serialization, thread safety and prevent reflective attacks, is a recommended concise and reliable method. Different implementation methods can be selected according to specific needs
Java Optional example
Jul 12, 2025 am 02:55 AM
Optional can clearly express intentions and reduce code noise for null judgments. 1. Optional.ofNullable is a common way to deal with null objects. For example, when taking values ??from maps, orElse can be used to provide default values, so that the logic is clearer and concise; 2. Use chain calls maps to achieve nested values ??to safely avoid NPE, and automatically terminate if any link is null and return the default value; 3. Filter can be used for conditional filtering, and subsequent operations will continue to be performed only if the conditions are met, otherwise it will jump directly to orElse, which is suitable for lightweight business judgment; 4. It is not recommended to overuse Optional, such as basic types or simple logic, which will increase complexity, and some scenarios will directly return to nu.
How to fix java.io.NotSerializableException?
Jul 12, 2025 am 03:07 AM
The core workaround for encountering java.io.NotSerializableException is to ensure that all classes that need to be serialized implement the Serializable interface and check the serialization support of nested objects. 1. Add implementsSerializable to the main class; 2. Ensure that the corresponding classes of custom fields in the class also implement Serializable; 3. Use transient to mark fields that do not need to be serialized; 4. Check the non-serialized types in collections or nested objects; 5. Check which class does not implement the interface; 6. Consider replacement design for classes that cannot be modified, such as saving key data or using serializable intermediate structures; 7. Consider modifying
