Java 7
Features:
In Java SE
7 and later, any number of underscore characters (
_)
can appear anywhere between digits in a numerical literal. This feature enables
you, for example. To separate groups of digits in numeric literals, which can
improve the readability of your code.
For
instance, if your code contains numbers with many digits, you can use an
underscore character to separate digits in groups of three, similar to how you
would use a punctuation mark like a comma, or a space, as a separator.
Example:
package com.jsl.core;
public class Numbers {
public static void main(String[] args)
{
long
cardno=4214920316734659l;
long
ccno=4214_9203_1673_4659l;
System.out.println(cardno);
System.out.println(ccno);
}
}
You can place underscores only between digits; you cannot place
underscores in the following places:
At the beginning or end of a number
Adjacent to a decimal point in a floating point literal
Prior to
an F or L suffix
In positions where a string of digits is
expected
Diamond
Java 1.6 we must write
the
List<Product> list6=new
ArrayList<Product>();
From java 1.7
List<Product> list7=new
ArrayList< >();
package com.jsl.core;
import java.util.ArrayList;
import java.util.List;
class Product{
String
name;
public Product(String
name){
this.name=name;
}
@Override
public String toString() {
return "The product
name is :"+name;
}
}
public class Numbers {
public static void main(String[] args)
{
List<Product>
list6=new
ArrayList<Product>();
list6.add(new Product("Laptop"));
list6.add(new Product("Monitor"));
System.out.println(list6);
/* From java 1.7 we
can use */
List<Product>
list7=new ArrayList<>();
list7.add(new Product("Laptop"));
list7.add(new Product("Monitor"));
System.out.println(list7);
}
}
Catch with multiple exceptions
Since Java 7 you can write it like this, which makes our lives a lot
easier:
package com.jsl.core;
public class Numbers {
public static void main(String[] args)
{
try{
String
name="Krish";
System.out.println(name.substring(2,8));
int res=10/0;
System.out.println(res);
}catch(StringIndexOutOfBoundsException | ArithmeticException |
NullPointerException
e){
e.printStackTrace();
}
}
}
String with switch statement
Since
Java 7 one can use string variables in switch clauses. Here is an example:
package com.jsl.core;
public class Numbers {
public static void main(String[] args)
{
String
month="Mar";
switch(month){
case "Jan":System.out.println("Jan");
break;
case "Feb":System.out.println("Feb");
break;
case "Mar" : System.out.println("Mar");
break;
default :System.out.println("Default
");
}
}
}
Try with resource
handling
The compiler detects unhandled exceptions thrown by
automatic close() invocation on a resource.
package com.jsl.core;
import
java.io.BufferedReader;
import java.io.FileReader;
import java.io.IOException;
public class Numbers {
public static void main(String[] args)
{
try(BufferedReader bis =new BufferedReader(new FileReader("welcome.txt"))){
String
message=null;
while((message=bis.readLine())!=null){
System.out.println(message);
}
}catch (IOException e) {
e.printStackTrace();
}
}
}
