Difference Between If and Else If?

The difference is that if the first if is true, all of the other else ifs won't be executed, even if they do evaluate to true. If they were individual ifs, nevertheless, all of the ifs will be executed if they evaluate to true.

If you have used multiple if statements then if the condition is true all will be executed. If you have used if and else if combination only one will be executed where first comes the true value

// if condition true then all will be executed
if(condition) {
    System.out.println("First if executed");
}

if(condition) {
    System.out.println("Second if executed");
}

if(condition) {
    System.out.println("Third if executed");
}


// only one will be executed 

if(condition) {
   System.out.println("First if else executed");
}

else if(condition) {
   System.out.println("Second if else executed");
}

else if(condition) {
  System.out.println("Third if else executed");
}

if(i == 0) ... //if i = 0 this will work and skip the following else-if statements
else if(i == 1) ...//if i not equal to 0 and if i = 1 this will work and skip the following else-if statement
else if(i == 2) ...// if i not equal to 0 or 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 the i == 0 check, this if condition is checked
if(i == 2) ...//regardless of the i == 0 and i == 1 check, this if condition is checked

For the first case: once an else if (or the first if) succeeds, none of the remaining else ifs or elses will be tested. However in the second case every if will be tested even if all of them (or one of them) succeeds.