Java - Random Helpful Tips

• Ternary Operator

This  will to reduce line number of  code . 

condition ? ifConditionTrueWhatShouldHappen : ifConditionFalseWhatShouldHappen

 This can  be use instead of ,Normal if  and  else .

•  Substring

•     public String substring(int startIndex) : 

   This method returns new String object containing the substring of the given string from specified     startIndex (inclusive). 

•     public String substring(int startIndex, int endIndex):  

  This method returns new String object containing the substring of the given string from specified     startIndex   to    endIndex (exclusive).

  Index starts  from 0  .Returns index where found, or -1 if not found 

ex :-  

String text = "Here there everywhere";

int a =text.indexOf("there");   // a is 5

int b =text.indexOf("er"); // b is 1 

int c =text.indexOf("eR"); // c is -1, "eR" is not found

•  For Checking Null

  if(foo != null && foo.bar()) {
     someStuff();
  }

  will use short-circuit evaluation, meaning it ends if the first condition of a logical AND is false.            
•  The && and || operators "short-circuit", meaning they don't evaluate the right hand side if it isn't        necessary. The & and | operators, when used as logical operators, always evaluate both sides.

• Variable Arguments (Varargs) in Java
   

• There can be only one variable argument in a method.
• Variable argument (varargs) must be the last argument.
• ex:-
  // Java program to demonstrate varargs

  class Test1

  {

      // A method that takes variable number of intger

      // arguments.

      static void fun(int ...a)

      {

          System.out.println("Number of arguments: " + a.length);

          // using for each loop to display contents of a

          for (int i: a)

              System.out.print(i + " ");

          System.out.println();

      }

      // Driver code

      public static void main(String args[])

      {

          // Calling the varargs method with different number

          // of parameters

          fun(100);         // one parameter

          fun(1, 2, 3, 4);  // four parameters

          fun();            // no parameter

      }

  }