The difference between final, finally, and finalize in Java
Feb 19, 2024 pm 12:16 PM
The difference between final, finally, and finalize in Java requires specific code examples
In Java programming, we often encounter the three key points of final, finally, and finalize Words that, although spelled similarly, have different meanings and usage. This article will explain the differences between these three keywords in detail and give code examples to help readers better understand.
1. Final keyword
The final keyword can be used for classes, methods and variables. Its function is to make the modified class, method or variable immutable.
- Final class:
The final modified class means that the class cannot be inherited, that is, its subclasses cannot exist.
Sample code:
final class A {
// class implementation
}
// 以下代碼會報錯，無法繼承final類A
class B extends A {
// class implementation
}- final method:
The final modified method means that the method cannot be overridden by subclasses.
Sample code:
class A {
final void foo() {
// method implementation
}
}
class B extends A {
@Override
void foo(){ //以下代碼會報錯，無法重寫final方法
// method implementation
}
}- final variable:
The variable modified by final means that the value of the variable cannot be changed, that is, it is a constant. Final variables can be initialized when declared or in the constructor.
Sample code:
class A {
final int x = 10; //聲明時初始化
final int y;
A(){
y = 20; //在構(gòu)造方法中初始化
}
}
class B {
void foo() {
final int z = 30; //局部變量，必須在聲明時初始化
// method implementation
}
} 2. Finally keyword
The finally keyword is often used in the try-catch-finally statement block to ensure that no matter whether an exception occurs or not, finally All code in the block will be executed. The finally block is usually used to release resources or perform some necessary cleanup work.
Sample code:
try {
// 可能發(fā)生異常的代碼
}
catch (Exception e) {
// 異常處理邏輯
}
finally {
// 最終執(zhí)行的代碼，無論是否發(fā)生異常，都會執(zhí)行
// 釋放資源或者其他清理工作
}3. Finalize method
The finalize() method is the garbage collection method of an object. Before the object is recycled by the garbage collector, the garbage collector will call this method. method. This method is usually used to release underlying resources related to the object. However, the finalize() method is not guaranteed to be executed in time, so it is not recommended to use this method to release important resources.
Sample code:
class A {
// 對象的垃圾回收方法
protected void finalize() throws Throwable {
// 釋放與對象相關的底層資源
super.finalize();
}
}
public static void main(String[] args) {
A obj = new A();
obj = null; // 將對象置為null，讓垃圾回收器回收
System.gc(); // 手動觸發(fā)垃圾回收
}To sum up, the three keywords final, finally and finalize have different meanings and usages in Java. final is used to modify classes, methods and variables, indicating that they are immutable; finally is used in try-catch-finally statement blocks to ensure that the code in it will be executed regardless of whether an exception occurs; the finalize() method is the garbage collection of an object Method, called before the object is recycled. Understanding their differences and correct usage is very helpful for writing high-quality, easy-to-maintain Java code.
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