SQOL Query:
SELECT COUNT(AssigneeId) FROM PermissionSetAssignment WHERE Assignee.isActive = true AND PermissionSet.Name = 'My_Sample_PermissionSet'
Note: Change the Permission Set API Name as per your requirement.
SOQL Query:
SELECT COUNT(Id) FROM User WHERE IsActive = true AND Profile.Name = 'System Administrator'
Note: Change the Profile Name as per your requirement.
In Salesforce there are two methods to set password and to reset password for a user.
resetPassword(Id userId, Boolean sendUserEmail): This method resets the password for the specified user. When the user logs in with the new password, they are prompted to enter a new password, and to select a security question and answer if they haven’t already. If you specify true for sendUserEmail, the user is sent an email notifying them that their password was reset. A link to sign onto Salesforce using the new password is included in the email.
setPassword(Id userId, String password): Sets the password for the specified user. When the user logs in with this password, they are not prompted to create a new password.
Sample Code:
List<User> users = new List<User>();
String username = 'test@test.com';
users = Database.Query('SELECT Id, Name FROM User WHERE UserName =: username');
for(User u : users){
//For reset User password
System.resetPassword(u.Id, true);
//For set User password
//System.setPassword(u.Id, 'Test@1234');
}