threads_finishing.rb

threads = []
3.times do |i|
  threads << Thread.new do
    3.times do |j|
      puts "Thread #{i} says #{j} (#{Thread.current})"
      sleep 0.1
    end
  end
end

10.times do |i|
  puts "Lets let other threads finish #{i + 1}"
  sleep 0.1
end

# Result
# Thread 0 says 0 (#<Thread:0x007fb149954708>)
# Thread 1 says 0 (#<Thread:0x007fb1499545f0>)
# Lets let other threads finish 1
# Thread 2 says 0 (#<Thread:0x007fb14982bac0>)
# Thread 1 says 1 (#<Thread:0x007fb1499545f0>)Thread 0 says 1 (#<Thread:0x007fb149954708>)
# Thread 2 says 1 (#<Thread:0x007fb14982bac0>)
# Lets let other threads finish 2
#
# Lets let other threads finish 3
# Thread 0 says 2 (#<Thread:0x007fb149954708>)
# Thread 1 says 2 (#<Thread:0x007fb1499545f0>)
# Thread 2 says 2 (#<Thread:0x007fb14982bac0>)
# Lets let other threads finish 4
# Lets let other threads finish 5
# Lets let other threads finish 6
# Lets let other threads finish 7
# Lets let other threads finish 8
# Lets let other threads finish 9
# Lets let other threads finish 10