JDK8簡化if-else

簡化if-else

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User user = ... if (user != null) { String userName = user.getUserName(); if (userName != null) { return userName.toUpperCase(); } else { return null; } } else { return null; }

上面的代碼可以簡化成：

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User user = ... Optional<User> userOpt = Optional.ofNullable(user); return user.map(User::getUserName) .map(String::toUpperCase) .orElse(null);