== and != (not equal) can be used to compare values. They return true or false boolean values.
= sign changes the value of a variable. Two == equal signs are used to test if a variable holds a certain value, without changing its value!
int and reference types like Dog are compared with == in a physical model of Java memory.
=) is used for assigning a value and 2 equal signs (==) for testing values. Then, add 3 more lines of code that sets year to 15 and prints out whether age is equal to year and whether age is not equal to year.
== or != to test if two reference values, like Turtle and String objects, refer to the same object. In the figure below, we are creating two separate Turtle objects called juan and mia. They do not refer to same object or turtle. Then, we create a reference variable called friend that is set to mia. The turtle mia will have two ways (references or aliases) to name her – she’s both mia and friend, and these variables refer to the same object (same Turtle) in memory. If two reference variables refer to the same object like the turtle on the right in the image below, the test with == will return true which you can see in the code below.
< to compare strings, Java only uses these operators for numbers, and uses the methods compareTo and equals for comparing String values.
< Less Than
> Greater Than
<= Less than or equal to
>= Greater than or equal to
== Equals
!= Does not equal
< and > apart, think of < and > as arrows where the pointy end should point to the smaller value. If < (less than) points towards a smaller number on the left, then it evaluates to true. On the other hand a > (greater than) expression will be true only if the smaller number is on the right hand side. Or maybe you prefer the “hungry alligator” mnemonic beloved by elementary school teachers—think of < and > as the mouths of hungry alligators which always want to eat the bigger number; a < or > expression is only true if the alligator is in fact about to eat the bigger number.
<= and >=, just write them in the same order you would say them in English: “less than or equal to” not “equal to or less than”.
// Test if a number is positive
(number > 0)
//Test if a number is negative
(number < 0)
//Test if a number is even by seeing if the remainder is 0 when divided by 2
(number % 2 == 0)
//Test if a number is odd by seeing if there is a remainder when divided by 2
(number % 2 != 0)
//Test if a number is a multiple of x (or divisible by x with no remainder)
(number % x == 0)
% is a remainder operator and not a true mathematical modulo operator, you can’t check if a number is odd with the expression num % 2 == 1.
true if num is positive and odd and false when num is even, both of which are correct. But if num is negative and odd, its remainder when divided by 2 is -1, not 1 and this expression will evaluate to false. Thus you should always use num % 2 != 0 to check if num is odd.
== and != to determine whether the values are the same. With primitive types, this compares the actual primitive values. With reference types, this compares the object references.
<, >, <=, >=) to determine the relationship between the values.
Boolean value of true or false.
% can be used to test for divisibility by a number. For example, num % 2 == 0 can be used to test if a number is even.
boolean x = (5 % 3 == 0) == (3 > 5);
(x >= 10) == (y < 12)
