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Static Block In Java:
A static block is similar to the init block with with
few differences. A static block executes only once at the time of class loading. Let’s
take a scenario where I want to initialize my static data members dynamically. In
a simple java program there is no place which ensures one time execution during class loading,
we have main() method but this method executes after class is loaded. So, to
overcome this problem, the static block is introduced.
Example:
Let’s take a simple example which initializes the
static data members dynamically.
class Temp
{
static int x;
static{
try{
System.out.println("Executing
Static Block: Please enter any number: ");
x = System.in.read();
}
catch(Exception e)
{
e.printStackTrace();
}
}
Temp()
{
System.out.println("Default
constructor executed.");
}
Temp(int x)
{
System.out.println("Parameterized
constructor executed.");
}
public static void main(String
args[])
{
Temp
temp1 = new Temp();
Temp
temp2 = new Temp(20);
System.out.println("x =
" + Temp.x);
}
}
Output:
Executing Static Block: Please
enter any number: 90
Default constructor executed.
Parameterized constructor
executed.
x =
57
Let’s take another example of static block:
Temp.java
class Temp
{
static Demo d;
static{
d = new Demo();
}
}
Demo.java
public class Demo
{
void show (int x)
{
System.out.println("x =
" + x);
}
public static void main(String
args[])
{
Temp.d.show(20);
}
}
Output:
x = 20
in above example Temp.d.show(20) is equivalent
to famous System.out.println(20), So System.out.println is internally implemented
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