非存取修飾符是 Java 7 中引入的關鍵字,用於通知 JVM 有關類別的行為、方法或變數等的資訊。這有助於引入其他功能,例如用於指示變數不能被初始化兩次的 Final 關鍵字。總共引入了 7 個非訪問修飾符。
以下是 Java 中非存取修飾符的類型:
廣告 該類別中的熱門課程 JAVA 掌握 - 專業化 | 78 課程系列 | 15 次模擬測驗此修飾符可應用於:
代碼:
final class Honda{ public void myFun1(){ System.out.println("Honda Class"); } } class Bike extends Honda{ public void myFun1(){ System.out.println("Bike Class"); } }
輸出:
代碼:
class Honda{ public final void myFun1(){ System.out.println("Honda Class"); } } class Bike extends Honda{ public void myFun1(){ System.out.println("Bike Class"); } }
輸出:
代碼:
public abstract class MyActivity{ public MyActivity(){ } public final String myFun1(){ } }
範例: public abstract void fun1();
代碼:
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"); } }
輸出:
此關鍵字有助於防止多個執行緒同時存取一個方法,從而同步程式流程並使用多執行緒功能得出所需的結果。
代碼:
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"); } } }
輸出:
此變數用於記憶體管理,也是載入類別時首先引用的變數。這些成員受到班級層級的待遇;因此,不能使用物件來呼叫它們;相反,類別的名稱用於引用它們。
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:
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"); } }
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:
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:
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.
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 –
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