step 1: code block inside A1
step 2: constructor inside A1
method m in A1, i = 1
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step 1: code block inside A1
step 2: constructor inside A1
method m in B1, i = 1 j = 0
step 3: code block inside B1
step 4: constructor inside B1
method m in B1, i = 1 j = 2