Python转Java场景下if条件表达式求值含义咨询

Hey there! Let's unpack this Python line so you can understand exactly what it's doing, making your Java translation straightforward.

First, let's split the condition into its core parts:

• all(cId in historyCId[rOBE] for cId in cIds): This is a generator expression wrapped in Python's built-in all() function
• not all(...): We're inverting the result of the all() check

What each part does: #

1. The generator expression: (cId in historyCId[rOBE] for cId in cIds)

   • It loops through every cId in your cIds JSONArray
   • For each cId, it checks if that cId exists in the collection stored under the key rOBE in your historyCId HashMap (so historyCId[rOBE] must be some kind of iterable/collection like a list or set)
   • Each check returns a boolean: True if the cId is present, False otherwise

2. The all() function:

   • Python's all() takes an iterable of booleans and returns True only if every single boolean in the iterable is True
   • If even one boolean is False, all() returns False

3. The not operator:

   • This flips the result of the all() check. So:
     • If all(...) returns True (all cIds are present in historyCId[rOBE]), not all(...) becomes False → the if block won't run
     • If all(...) returns False (at least one cId is missing from historyCId[rOBE]), not all(...) becomes True → the if block will execute

Quick summary of the condition's outcome: #

The if statement will run when at least one cId from cIds is NOT present in the collection stored under rOBE in historyCId.

For context, in Java you'd replicate this by:

• Getting the collection from historyCId.get(rOBE) (make sure to handle cases where rOBE isn't a key in the HashMap!)
• Iterating over each element in cIds
• Checking if each element exists in the collection
• If any element is missing, trigger the logic inside the if block

内容的提问来源于stack exchange，提问作者Syndrite