Mysql password expired. Can't connect

So I finally found the solution myself.

Firstly I went into terminal and typed:

mysql -u root -p

This asked for my current password which I typed in and it gave me access to provide more mysql commands. Anything I tried from here gave this error:

ERROR 1820 (HY000): You must reset your password using ALTER USER statement before executing this statement.

This is confusing because I couldn't actually see a way of resetting the password using ALTER USER statement, but I did find another simple solution:

SET PASSWORD = PASSWORD('xxxxxxxx');

First, I use:

 mysql -u root -p

Giving my current password for the 'root'. Next:

mysql> ALTER USER `root`@`localhost` IDENTIFIED BY 'new_password',
       `root`@`localhost` PASSWORD EXPIRE NEVER;

Change 'new_password' to a new password for the user 'root'.
It solved my problem.

mysqladmin -u [username] -p password worked for me on OS X El Capitan and MySQL 5.7.12 Community Server. Example:

$ /usr/local/mysql/bin/mysqladmin -u root -p password
Enter password:
New password:
Confirm new password:
Warning: Since password will be sent to server in plain text, use ssl connection to ensure password safety.

This is similar to pavan sachi's answer, but with password prompts.

My error was "#1862 - Your password has expired. To log in you must change it using a client that supports expired passwords." at phpMyAdmin login screen first time.