java 7 features

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();

              }

                          

              }

}