Pengubah Suai Bukan Akses di Java

Pengubah Bukan Akses ialah kata kunci yang diperkenalkan dalam Java 7 untuk memberitahu JVM tentang gelagat, kaedah atau pembolehubah kelas, dsb. Itu membantu memperkenalkan fungsi tambahan, seperti kata kunci akhir yang digunakan untuk menunjukkan bahawa pembolehubah tidak boleh dimulakan dua kali. Terdapat sejumlah 7 pengubah bukan akses diperkenalkan.

1. Statik
2. Akhir
3. Abstrak
4. Disegerakkan
5. sementara
6. strictfp
7. asli

Jenis Pengubah Suai Bukan Akses dalam Java

Di bawah ialah jenis Pengubah Suai Bukan Akses dalam Java:

IKLAN Kursus Popular dalam kategori ini JAVA MASTERY - Pengkhususan | 78 Siri Kursus | 15 Ujian Olok-olok

1. Pengubah Bukan Akses Akhir

Pengubah suai ini boleh digunakan dengan:

1. Kelas
2. Kaedah
3. Pembolehubah Instance
4. Pembolehubah Setempat
5. Hujah kaedah

• Kelas Akhir: Kata Kunci Akhir digunakan dengan kelas apabila kita ingin mengehadkan warisannya oleh mana-mana kelas lain. Contohnya, Jika kita mempunyai Honda kelas akhir, maka sebarang percubaan untuk melanjutkan kelas ini boleh membawa kepada ralat masa kompilasi.

Kod:

final class Honda{
public void myFun1(){
System.out.println("Honda Class");
}
}
class Bike extends Honda{
public void myFun1(){
System.out.println("Bike Class");
}
}

Output:

• Kaedah Akhir: Kata Kunci Akhir digunakan untuk menunjukkan Java Runtime Environment bahawa kaedah ini tidak dimaksudkan untuk ditindih dalam mana-mana subkelasnya.

Kod:

class Honda{
public final void myFun1(){
System.out.println("Honda Class");
}
}
class Bike extends Honda{
public void myFun1(){
System.out.println("Bike Class");
}
}

Output:

• Pembolehubah Akhir: Kata kunci akhir digunakan dengan pembolehubah untuk menyekat sebarang pengubahsuaian pada nilai pembolehubah, dengan itu menunjukkan JVM untuk menganggapnya sebagai pemalar. Ini bermakna pembolehubah akhir boleh dimulakan sekali sahaja.

2. Pengubah Suai Abstrak Bukan Akses

• Kelas Abstrak: Kelas diisytiharkan sebagai abstrak untuk menunjukkan bahawa kelas ini tidak boleh dijadikan instantiated, yang bermaksud tiada objek boleh dibentuk untuk kelas ini tetapi boleh diwarisi. Namun, kelas ini mempunyai pembina yang akan dipanggil di dalam pembina subkelasnya. Ia boleh mengandungi kaedah abstrak dan juga akhir, dengan kaedah abstrak akan ditindih dalam subkelas.

Kod:

public abstract class MyActivity{
public MyActivity(){
}
public final String myFun1(){
}
}

• Kaedah Abstrak: Kaedah abstrak ialah kaedah tanpa sebarang definisi. Ia mengandungi hanya tandatangan kaedah dan bertujuan untuk menunjukkan bahawa ini perlu ditindih dalam subkelas.

Contoh: abstrak awam void fun1();

Kod:

abstract class Electronics
{
abstract void display();
abstract void display(String msg);
}
class Computers extends Electronics
{
@Override
void display() {
System.out.println("Abstract method is called");
}
@Override
void display(String txt) {
System.out.println(txt);
}
}
public class AbstractDemo {
public static void main(String[] args) {
Computers obj=new Computers();
obj.display();
obj.display("Method with arguments");
}
}

Output:

3. Pengubah Suai Bukan Akses Disegerakkan

Kata kunci ini membantu menghalang capaian satu kaedah oleh berbilang utas secara serentak, dengan itu menyegerakkan aliran program dan mengeluarkan hasil yang diingini menggunakan ciri multithreading.

Kod:

class Person1
{
public synchronized void sendFun(String txt)
{
System.out.println("Sending message\t" + txt );
try
{
Thread.sleep(1000);
}
catch (Exception e)
{
System.out.println("Thread interrupted.");
}
System.out.println("\n" + txt + "Sent");
}
}
class DemoThread extends Thread
{
private String txt;
Person1  person;
DemoThread(String m,  Person1 obj)
{
txt = m;
person = obj;
}
public void run()
{
synchronized(person)
{
person.sendFun(txt);
}
}
}
public class HelloWorld
{
public static void main(String args[])
{
Person1 snd = new Person1();
DemoThread S1 =
new DemoThread( " Hi " , snd );
DemoThread S2 =
new DemoThread( " Bye " , snd );
S1.start();
S2.start();
// wait for threads to end
try
{
S1.join();
S2.join();
}
catch(Exception e)
{
System.out.println("Interrupted");
}
}
}

Output:

4. Pengubahsuai Bukan Akses Statik

Pembolehubah ini digunakan untuk pengurusan memori dan perkara pertama dirujuk semasa memuatkan kelas. Ahli-ahli ini dilayan pada peringkat kelas; oleh itu, mereka tidak boleh dipanggil menggunakan objek; sebaliknya, nama kelas digunakan untuk merujuk kepada mereka.

• Static Variable: If a variable is declared as static, then only a single copy of the variable is created and shared among all the objects. Thus any change made to the variable by one object will be reflected in other others. Therefore,  the variables that hold value on the class level is declared as static.
• Static Class: Static keyword can only be used with nested classes.
• Static Methods: Since Static Methods are referenced by class name thus can only access static member variables and other static methods. Also, these methods cannot be referred to using this or super pointer. The main method is the most common example of a static method that always get loaded while its class is being loaded.
• Static Block: This is said to be a block being used to perform certain operations while class is being loaded. Since it is static thus can use only static members of the class.

Code:

public class Demo
{
// static variable
static int x = 10;
static int y;
//static class
public static class DemoInnerClass{
static int z=10;
}
// static block
static {
System.out.println("Static block initialized.");
y = x + 4;
}
//static method
public static void main(String[] args)
{
System.out.println("from main");
System.out.println("Value of x : "+x);
System.out.println("Value of y : "+y);
System.out.println("Value of z : "+DemoInnerClass.z);
}
}

Output:

5. Native Non Access Modifier

The native keyword is used only with the methods to indicate that the particular method is written in platform -dependent. These are used to improve the system’s performance, and the existing legacy code can be easily reused.

Note: Static, as well as abstract methods, cannot be declared as native.

Example: Consider a function myfun1 in class NativeDemo that is written in C++. To use this code, we will create a link library mylib1 and load it using the class’s static block.

public class DateTimeUtils {
public native String getSystemTime();
static {
System.loadLibrary("nativedatetimeutils");
}
}

6. Strictfp Non-Access Modifier

• Strictfp Class / Method: This keyword is used to ensure that results from an operation on floating-point numbers brings out the same results on every platform. This keyword can not be used with abstract methods, variables or constructors as these need not contain operations.

Code:

public class HelloWorld
{
public strictfp double calSum()
{
double n1 = 10e+07;
double n2 = 9e+08;
return (n1+n2);
}
public static strictfp void main(String[] args)
{
HelloWorld t = new HelloWorld ();
System.out.println("Result is -" + t.calSum());
}
}

Output:

7. Transient Non-Access Modifier

While transferring the data from one end to another over a network, it must be serialised for successful receiving of data, which means convert to byte stream before sending and converting it back at receiving end. To tell JVM about the members who need not undergo serialization instead of being lost during transfer, a transient modifier comes into the picture.

Syntax:

private transient member1;

Code:

import java.io.*;
class Demo implements Serializable
{
int x = 10;
transient int y = 30;
transient static int z = 40;
transient final int d = 50;
public static void main(String[] args) throws Exception
{
Demo input = new Demo();
FileOutputStream tos = new FileOutputStream("abc.txt");
ObjectOutputStream tin = new ObjectOutputStream(tos);
tin.writeObject(input);
FileInputStream fis = new FileInputStream("abc.txt");  ObjectInputStream ois = new ObjectInputStream(fis);
Demo output = (Demo)ois.readObject();
System.out.println("x = " + output.x);
System.out.println("y = " + output.y);
System.out.println("z = " + output.z);
System.out.println("d = " + output.d);
}
}

Output:

Conclusion

Non-access modifiers are the type of modifiers that tell JVM about the behavior of classes, methods, or variables defined and prepared accordingly. It also helps in synchronizing the flow as well as displaying similar results from operations being performed irrespective of the platform used for execution.

Recommended Article

This is a guide to Non Access Modifiers in Java. Here we discuss the Types of Non Access Modifiersand their methods and code implementation in Java. You can also go through our other suggested articles to learn more –

1. Layout in Java
2. Java Compilers
3. Merge Sort In Java
4. Java BufferedReader

Atas ialah kandungan terperinci Pengubah Suai Bukan Akses di Java. Untuk maklumat lanjut, sila ikut artikel berkaitan lain di laman web China PHP!