Write all the program in JAVA:

$1$: Write a program that initializes an integer variable and checks if the number is positive, negative, or zero using if$-$else conditions.

$2$: Create a program where two variables, age and country, are predefined. Use AND and OR operations to check if the person is over $18$ and from a specific country $($e$.$g$.,$ "USA"$),$ then print an appropriate message.

$3$: Write a program to check if a predefined number is NOT equal to a given number $($e$.$g$.,15).$ If the condition is true, print $$Numbers are not equal,$$ otherwise print $$Numbers are equal.$$

$4$: Write a program that checks if a predefined number is even or odd using the modulus operator.