遍历iterator迭代器remove的问题

朴灿烈づ我的快乐病毒、 2022-12-27 14:06 192阅读 0赞

# 开发小问题-遍历iterator迭代器remove的问题 #

在实际场景中使用迭代器遍历时，使用remove出现的问题，先作简单的记录，后续再深入研究。

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## 应用场景 ##

对一个ma作keyset()遍历，判断 value 为目标值时从map中剔除。

我的错误代码示例

@Test
        public void errorFuction() {
    
            Map<String, String> settleMap = new HashMap<>();
            settleMap.put("a", "aaaaa");
            settleMap.put("b", "bbbbb");
            settleMap.put("c", "bbbbb");
            Iterator<String> iterator = settleMap.keySet().iterator();
            while (iterator.hasNext()) {
                String key = iterator.next();
                log.info("key={}", key);
                String value = settleMap.get(key);
                if ("bbbbb".equals(value)) {
                    settleMap.remove(key);
                    log.info("removeKey={}",key);
                    continue;
                }
                log.info("value={}", value);
            }
    
            log.info("map={}",settleMap);
        }

具体报错

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3hpbnB6_size_16_color_FFFFFF_t_70][]

## 优化测试 ##

改正后的代码

@Test
        public void test() {
    
            Map<String, String> settleMap = new HashMap<>();
            settleMap.put("a", "aaaaa");
            settleMap.put("b", "bbbbb");
            settleMap.put("c", "bbbbb");
            Iterator<String> iterator = settleMap.keySet().iterator();
            while (iterator.hasNext()) {
                String key = iterator.next();
                log.info("key={}", key);
                String value = settleMap.get(key);
                if ("bbbbb".equals(value)) {
                    iterator.remove();
                    log.info("removeKey={}",key);
                    continue;
                }
                log.info("value={}", value);
            }
    
            log.info("map={}",settleMap);
        }

正确结果

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3hpbnB6_size_16_color_FFFFFF_t_70 1][]

[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3hpbnB6_size_16_color_FFFFFF_t_70]: /images/20221120/15db3b3dfdf04e37927a91161d8e69fd.png
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3hpbnB6_size_16_color_FFFFFF_t_70 1]: /images/20221120/7f3af8be3b5e497faaa2810aed00eae8.png