The deal, as reported by Sportsnet's Elliotte Friedman, has since been confirmed by the team.
As noted by Sportsnet's Chris Johnston, the Maple Leafs didn't retain any of Johnsson's salary in the trade, clearing up a $3.4-million cap commitment -- which was necessary to do after the team's signings of T.J. Brodie and Wayne Simmonds.
Anderson, who was originally selected by the New Jersey Devils 73rd overall in the 2016 NHL Draft, split the 2019-20 season between New Jersey and its AHL affiliate, the Binghamton Devils.
In 18 games with the Devils, he recorded four goals and two assists. Internationally, Anderson has represented the United States at the U17, U18 and U20 levels, capturing a gold medal at the 2017 world junior championships and a bronze medal in 2018.
Anderson was in the final year of a three-year contract with an average annual value of $925,000, and is now a restricted free agent with 10.2(c) status, as noted by Johnston. This means he is not eligible for an offer sheet, and will need to reach a new contract in Toronto.
The Devils, meanwhile, acquire Johnsson, who scored eight goals and added 13 assists in 43 games with the Maple Leafs last season.
Across his four-year tenure with Toronto, the 25-year-old scored 30 goals and 37 assists.
"Andreas is a hard-working, competitive forward who can slot up and down the lineup,” Tom Fitzgerald, the Devils general manager, wrote in a press release. “The overall versatility of his game will be a great complement to our centremen, with his skating, quickness and scoring touch.”