Java比较两个图

Question

在Java中，我想比较两个地图，如下所示，我们是否有现有的API可以做到这一点？

谢谢

Map<String, String> beforeMap ;
beforeMap.put("a", "1");
beforeMap.put("b", "2");
beforeMap.put("c", "3");

Map<String, String> afterMap ;
afterMap.put("a", "1");
afterMap.put("c", "333");

//--- it should give me:
b is missing, c value changed from '3' to '333'

Answer 1

我将使用Set的removeAll（）功能来设置键的差异，以查找添加和删除的内容。可以通过使用设置为HashMap的条目进行设置差异来检测实际更改。Entry同时使用键和值实现equals（）。

Set<String> removedKeys = new HashSet<String>(beforeMap.keySet());
removedKeys.removeAll(afterMap.keySet());

Set<String> addedKeys = new HashSet<String>(afterMap.keySet());
addedKeys.removeAll(beforeMap.keySet());

Set<Entry<String, String>> changedEntries = new HashSet<Entry<String, String>>(
        afterMap.entrySet());
changedEntries.removeAll(beforeMap.entrySet());

System.out.println("added " + addedKeys);
System.out.println("removed " + removedKeys);
System.out.println("changed " + changedEntries);

输出量

added []
removed [b]
changed [c=333]