在Java 中操作 Map时高效遍历和安全删除数据的方法

Map<String, Integer> map = new HashMap<>();
map.put("key1", 5);
map.put("key2", 3);
Iterator<Map.Entry<String, Integer>> iterator = map.entrySet().iterator();
while (iterator.hasNext()) {
    Map.Entry<String, Integer> entry = iterator.next();
    String key = entry.getKey();
    Integer value = entry.getValue();
    System.out.println(key + ": " + value);
}

map.forEach((key, value) -> {
    System.out.println(key + ": " + value);
});

for (Map.Entry<String, Integer> entry : map.entrySet()) {
    String key = entry.getKey();
    Integer value = entry.getValue();
    // ...
}

map.entrySet().stream()
    .filter(entry -> entry.getValue() > 3) // 过滤条件
    .forEach(entry -> {
        System.out.println(entry.getKey();
    });

Iterator<Map.Entry<String, Integer>> iterator = map.entrySet().iterator();
while (iterator.hasNext()) {
    Map.Entry<String, Integer> entry = iterator.next();
    if (entry.getValue() < 3) {
        iterator.remove();
    }
}

map.entrySet().removeIf(entry -> entry.getValue() < 3);

map.remove("key1");

Map<String, Integer> map = new HashMap<>(Map.of(
    "key1", 5,
    "key2", 3,
    "key3", 2
));
// 遍历并删除 value < 3
map.entrySet().removeIf(entry -> entry.getValue() < 3);
// 输出结果：{key1=5, key2=3}
System.out.println(map);