Question:
class Simple{
public static void main(String
args[]){
String s=50+30+"Sachin"+40+40;
System.out.println(s);//80Sachin4040
}
}
Wednesday, May 14, 2014
What is the output for the below piece of Code? #2
Question:
class Simple{
public static void main(String
args[]){
String s=50+30+"Sachin"+40+40;
System.out.println(s);//80Sachin4040
}
}
Output:
80Sachin4040What is the output for the below piece of Code? #1
Question :
public class StringTest
{
public static void main(String
args[])
{
String s = "sachin";
s.concat("tendulkar");
System.out.println(s);
}
}
Output:
sachinBecause String is immutable in Java.
Question :
public class StringTest
{
public static void main(String
args[])
{
String s = "sachin";
s=s.concat("tendulkar");
System.out.println(s);
}
}
Output:
sachintendulkarHere a new string "sachintendulkar" is created and 's' is made as a reference to this new string.
String object "sachin" still exist in the string constant pool.
Tuesday, May 13, 2014
static blank final variable
A static final variable that is not initialized at the time of
declaration is known as static blank final variable. It can be
initialized only in static block.
What is blank or uninitialized final variable?
A final variable that is not initialized at the time of declaration is known as blank final variable.
If you want to create a variable that is initialized at the time of creating object and once initialized may not be changed, it is useful. For example PAN CARD number of an employee.
It can be initialized only in constructor.
If you want to create a variable that is initialized at the time of creating object and once initialized may not be changed, it is useful. For example PAN CARD number of an employee.
It can be initialized only in constructor.
What if the static modifier is removed from the signature of the main method?
Program compiles. But at runtime throws an error "NoSuchMethodError".
Restrictions for static method
There are two main restrictions for the static method. They are:
- The static method can not use non static data member or call non-static method directly.
- this and super cannot be used in static context.
If no arguments are passed on the Commandline...
String array of main method will be empty, NOT NULL!
Is Empty .java file name a valid source file name?
YES.
- Save a java file as ".java"
- Compile it as "javac .java"
- Run it as "java className" [where className is the name of your java class within the file .java]
Memory Areas allocated by JVM
By Praveesh
9:59 PM
Class area,
Heap,
memory allocated by JVM,
native method stack,
program counter,
stack
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- Class (Method) Area - Stores class structures such as runtime constant pool, method data, method code etc.
- Heap - Runtime memory area where objects are allocated.
- Stack - Holds local variables, method call/retun data.
- Program Counter Register - Stores address of JVM instruction currently being executed.
- Native Method Stack - Stores all native methods used in the application.