This article describes a technique for overriding the equals method that preserves the contract of equals even when subclassses of concrete classes add new fields. In Item 8 of Effective Java1, Josh Bloch describes the difficulty of preserving the equals contract when subclassing as a “fundamental problem of equivalence relations in object-oriented languages.” Bloch writes: There is no way to exte
文字列 文字列を数値に変換する list_to_integer("123"). % 123 list_to_integer("-10"). % -10 n進数の文字列を数値に変換する u は指定した基数で変換、# は文字列が表現している基数で変換します。 io_lib:fread("~16u", "100"). % {ok,[256],[]} io_lib:fread("~2u", "100abc"). % {ok,[4],[abc]} io_lib:fread("~36u", "100%%%"). % {ok,[1296],"%%%"} io_lib:fread("~#", "16#100"). % {ok,[256],[]} io_lib:fread("~#", "2#100abc"). % {ok,[4],[abc]} io_lib:fread("~#", "36#100%%%").
Before Java Specification Request (JSR) 223, Scripting for the Java Platform, (and its predecessor, the Bean Scripting Framework, or BSF), many languages were already communicating with Java. Some languages would take textual code as input from a Java program and return the evaluation result back. Others would keep references to objects in a Java program, invoke methods on those objects, or create
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