Iterating through/Updating HashMap

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Iterate through a HashMap [duplicate] 7 answers

How to efficiently iterate over each entry in a 'Map'? 38 answers

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利用地图：首先浏览其他收藏并进行操作。

for(String blacklisted : blacklist) {
    wordcounts.remove(blacklisted);
}
for(String mapping : mappings) {
    String oldKey =    // get old key
    String value = wordcounts.get(oldKey);
    wordcounts.remove(oldKey);
    wordcounts.put(mapping, value);
}

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Use Map.Entry.setValue to change the value of the mapping. If you want to remove the mapping, use setValue(null) use an Iterator .

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Don't try to remove items during the iteration or you'll get an exception out of the iterator. Best bet is to either

a) clone the map by iterating/copying into a new map or b) keeping track as you go along of items to be removed and removing them after you're done iterating.

If you're changing keys, same thing applies.. keep track as you go and do the remove/add after you're done iterating.

If you're just changing values, just go for it.

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