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Access Modifier:-There are four access modifiers are available in java .

public
private
protected
default

In java by default modifier is default if we are not using any modifier then by default access modifier will be default modifier.

Applicable access modifiers for outer classes are default and public only. We cannot use private or protected modifier for outer classes.

If we use private or protected modifier for outer class then compiler gives below error.

private  class Student1
{
}

C:\JAVATECH>javac Student1.java

Student1.java:1: error: modifier private not allowed here
private class Student1
        ^
1 error

protected class Student1
{
}

C:\JAVATECH>javac Student1.java
Student1.java:1: error: modifier protected not allowed here
protected class Student1
        ^
1 error

If we use default modifier than we will not face any problem, but if we use public modifier than file name must be public classname.java only.

Example1: - file name is A.java and public class name is Student.
public class Student
{
}

C:\JAVATECH>javac A.java
A.java:1: error: class Student is public, should be declared in a file named Student.java
public class Student
       ^
Example2: - file name is A.java contains two public classes names are Student and Test.

public class Student
{
}
public class Test
{
}

C:\JAVATECH>javac A.java
A.java:1: error: class Student is public, should be declared in a file named Student.java
public class Student
       ^
A.java:3: error: class Test is public, should be declared in a file named Test.java
public class Test
       ^
2 errors

Example3: - file name is Student.java contains two public classes names are Student and Test.
public class Student
{
}
public class Test
{
}
C:\JAVATECH>javac Student.java
Student.java:3: error: class Test is public, should be declared in a file named Test.java
public class Test

So in a java program we can use only one public class and any number of default classes but file must be saved by public class name.java.

Example3: - file name is Student.java contains one  public class names is Student and two default classes Test and Run.

public class Student
{
}
class Test
{
}
class Run
{
}

C:\JAVATECH>javac Student.java

C:\JAVATECH>


Program successfully compiled.


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