Types of Operators

1. Add/Sub:

If X and Y are integers or doubles then adds or subtracts the value of Y from X and if any X or Y is double then the result is double.
If X is a date and Y is an integer then it returns a new date that is incremented or decremented by the specified number of days.
If X s a DateTime and Y is an integer or double then it returns a new DateTime which is incremented or decremented by specified number of days with a fractional portion corresponding to a portion of the day.

Ex: main() {

Double d = 5.2;

DateTime dt = new DateTime.now();

DateTime finalDate = dt -d ;

System.debug(dt);

System.debug(finalDate);

}

Note: Only in case of ‘+’ if X is a string and Y is a string or any other type of non-null argument then it concatenates Y to the end of X.

2. Shorthand Operator:

|= (OR assignment operator):

If X(boolean) and Y(boolean) are both false then X remains false otherwise X is assigned true.

&= (AND assignment operator):

If X(boolean) and Y(boolean) are both true then X remains true otherwise X is assigned false.

3. Equality Operator(==):

If a value of X equals Y, the expression evaluates to true otherwise the expression evaluates to false.

Note: Unlike java(==), in apex it compares object value equality not reference equality except for user-defined types..

Note: String comparison using(==) is case insensitive.

Note: ID comparison using == is case sensitive.

User-defined types are compared by reference which means that the 2 objects are equal if they reference the same location in the memory.
You can override this default comparison behavior by equals() and hashcode() methods in your class to compare object values instead.

main()

{

Integer a[] = new Integer[5];

Integer b[] = new Integer[5];

for(Integer i=0; i<5; i++)

a[i]=i+1;

System.debug(a);

System.debug(b);

System.debug(a==b);

}

Note: Arrays(==) performs a deep check of all the values before returning its result. Likewise for collection and built-in apex objects.

Note: The comparison of any two values can never result in null though X and Y can be literal null.

Note: SOQL and SOSL use ‘=’ for their equality operator not ‘==’.

4. Exact Equality Operator(===):

If X and Y reference the exact same location in memory, the expression evaluates to true otherwise false.

main()

{

FirstClass fc = new FirstClass();

FirstClass fc2 = new FirstClass();

System.debug(if(fc===fc2));

}

5. Exact Inequality Operator(!==):

If X and Y do not reference the exact same location in emory, the expression evaluates to true otherwise false.

6. Relational Operators(<,>,<=,>=):

If X or Y equals null and are integers, doubles, dates or DateTimes then it will return false.
A non-null string or id value is always greater than a null value.
If X and Y are ids then, they must reference the same value otherwise a runtime error occurs.
If X or Y is an id and other value is a sting then the string is validated and treated as an id.
X and Y can not be boolean.

Id i1 = “——”;

Id i2 = “——”;

System.debug(i1>i2);