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From the link below, I know Java uses (hash & 0x7FFFFFFF) % tab.length to decide which slot of an array to put the {key, value} in.
My question is why Java first does hash & 0x7FFFFFFF? Is there any particular purpose?
Because
-1 % 10 == -1which you certainly don’t want for indexing into an array. Forcing the sign bit to 0 avoids this problem.