Notes on core java

1. Core Java
Debasish Pratihari
Type Casting:


Converting one type of data into another must
follow the rules of casting. If a conversion
results in the loss of precision, as in an int
value converted to a short, then the compiler
will issue an error message unless an explicit
cast is made.
a data type with lower precision (fewer bits)
can be converted to a type of higher precision
without explicit casting. To convert a higher
precision type to a lower precision, however,
an explicit cast is required or the compiler will
flag an error.
Primitive Type Conversion Table:
Note :




The symbol C indicates that an explicit
cast is required since the precision is
decreasing.
The symbol A indicates that the precision
is increasing so an automatic cast occurs
without the need for an explicit cast.
N indicates that the conversion is not
allowed.
The * asterisk indicates that the least
significant digits may be lost in the
conversion.
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2. Core Java
Debasish Pratihari
&& verses & :

The && operators perform Conditional-AND
operations on two Boolean expressions. These
operators exhibit "short-circuiting" behavior,
which means that the second operand is
evaluated only if needed.

The & operator do the same thing as && but it
does not exhibit "short-circuiting" behavior,
which means that the both operand are
evaluated always.
Enhanced for loop :
Example:1
class LoopDemo{
public static void main(String[] args){
int[] numbers = {1,2,3,4,5,6,7,8,9,10};
for (int item : numbers) {
System.out.println("Count is: " + item);
}
}
}
Example:2
class LoopDemo2{
public static void main(String[] args){
String [] names = {"Debasish","Sushant","Sidharth",
"Sanat","Nayaran"};
for (String name : names) {
System.out.println("Mr. " + name);
}
}
}
Controlling Statement in Java :



The break Statement
o Un-labeled
o Labeled
The continue Statement
o Un-labeled
o Labeled
The return Statement
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3. Core Java
Debasish Pratihari
Example of Un-labeled break :
class BreakTest{
public static void main(String args[]){
for( int i=1;i<=5;i++){
System.out.println("Outer loop"+i);
for(int j=10;j<=15;j++){
if(j==12)
break ;
System.out.println("Inner Loop"+j);
}
}
}
}
Example of Labeled break :
class BreakTest{
public static void main(String args[]){
stop:
for( int i=1;i<=5;i++){
System.out.println("Outer loop"+i);
for(int j=10;j<=15;j++){
if(j= =12)
break stop;
System.out.println("Inner Loop"+j);
}
}
}
}
Example of Un-labeled continue :
class ContinueTest{
public static void main(String args[]){
for( int i=1;i<=5;i++){
System.out.println("Outer loop"+i);
for(int j=10;j<=15;j++){
if(j= =12)
continue ;
System.out.println("Inner Loop"+j);
}
}
}
}
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4. Core Java
Debasish Pratihari
Example of labeled continue :
class ContinueTest{
public static void main(String args[]){
stop:
for( int i=1;i<=5;i++){
System.out.println("Outer loop"+i);
for(int j=10;j<=15;j++){
if(j==12)
continue stop;
System.out.println("Inner Loop"+j);
}
}
}
}
Variable Scope :
25% 
The Scope of a variable is the part of the program
over which the variable name can be referenced.
class x{
public static void main(String args[]){
int i;
{
int j;
//referring to i and j is ok here
}
//referring to i ok here
//referring to j is not ok here
}
}
Assertion :

An assertion is a statement in the JavaTM
programming language that enables you to test your
assumptions about your program.

Each assertion contains a boolean expression that
you believe will be true when the assertion executes.
If it is not true, the system will throw an error.

The assertion statement has two forms.
o assert Expression1 ;
o assert Expression1 : Expression2 ;
To activate assertions:
o java –ea Test

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