what's the difference between 'if else' and 'else if'? and how are they used?

Answer 1

Keep it simple. If tests the 1st condition, and if it meets the expression it will enter the code block. Else is the last option that will get executed if it didn't meet the first.

Think of if, else if, else if, else if, else as a switch condition:

if (this is right){
do this
}else if (test this one){
do this if it does
}else if (or maybe this){
do this instead
}else{
do this as the last resort or think default as none of the above worked
}

I would use a switch statement if gets too long, it's very similar to the above logic.

Answer 2

if(i == 0) ... //if i =0 this will work and skip following statement
else if(i == 1) ...//if i not equal to 0 and if i =1 this will work and skip following statement
else if(i == 2) ...// if i not equal to 0 and 1 and if i==2 the statement will execute

if(i == 0) ...//if i =0 this will work and check the following conditions also
if(i == 1) ...//regardless of i == 0 check, this if condition is checked
if(i == 2) ...//regardless of i == 0 and i == 2 check ,this if condition is checked