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Interface-4

Example11:-    Test.java

interface A
{
void disp();
}
class Test implements A
{
}

Output:-
C:\JAVATECH>javac Test.java
Test.java:5: error: Test is not abstract and does not override abstract method disp() in A
class Test implements A
^
1 error
Explanation: -Interface methods must be override in implemented class otherwise class must be declared as abstract.

Example12:-    Test.java

interface A
{
void disp();
}
abstract class Test implements A
{
}

Output:-
C:\JAVATECH>javac Test.java
C:\JAVATECH>javap Test
Compiled from "Test.java"
abstract class Test implements A {
  Test();
}

Example13:-    Test.java

interface A
{
void disp();
}
abstract class Test implements A
{
void disp()
{
System.out.println("Implemented method");
}
}

Output:-
C:\JAVATECH>javac Test.java
Test.java:7: error: disp() in Test cannot implement disp() in A
void disp()
     ^
  attempting to assign weaker access privileges; was public
1 error
Explanation: -by default interface methods are public and abstract so in the implemented class we cannot decrease visibility but we can increase.

Example14:-    Test.java

interface A
{
void disp();
}
abstract class Test implements A
{
public void disp()
{
System.out.println("Implemented method");
}
}

Output:-
C:\JAVATECH>javac Test.java
C:\JAVATECH>javap Test
Compiled from "Test.java"
abstract class Test implements A {
  Test();
  public void disp();

}

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