private long nextId = -1L 是什么意思?
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Declare a private long variable with the variable name nextId, initialize it, and assign the value to -1.
-1L means this is a long型常量
-1L
long型常量
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Declare a private long variable with the variable name nextId, initialize it, and assign the value to -1.
-1Lmeans this is along型常量