What makes these paragraphs an example of subject-by-subject writing? The paragraphs focus more on what is involved in becoming a judge as opposed to becoming a police officer.
The paragraphs focus first on becoming a police officer, second on becoming a judge, and finally on comparing the two.
The paragraphs compare two different careers, discussing criteria about each career one point at a time.
The paragraphs look at a variety of criteria involved in becoming a judge and a police officer, including salaries and the risk of on-the-job injuries.