Stream两个Map的value值进行相加/相减，并将合并数据集赋值给新Map
public static void main(String[] args) {
Map<String,Integer> map1 = new HashMap<>();
map1.put("1",1);
map1.put("2",2);
map1.put("3",3);
map1.put("4",4);
Map<String,Integer> map2 = new HashMap<>();
map2.put("1",1);
map2.put("2",2);
map2.put("3",3);
map2.put("5",5);
Map<String,Integer> map3 = new HashMap<>();
map3.put("1",2);
map3.put("2",4);
map3.put("3",6);
map3.put("5",8);
//以map2为基准，存放相加value值的数据集
Map<String, Integer> map4 = new HashMap<>(map2);
//以map1为基准，存放相减value值的数据集
Map<String, Integer> map5 = new HashMap<>(map1);
map1.forEach((key,value)->map4.merge(key,value,(v1,v2)->v1+v2));
System.out.println("原始数据集1: "+map1);
System.out.println("原始数据集2: "+map2);
System.out.println("原始数据集3: "+map3);
System.out.println("存放相加value值的数据集Map: "+map4);
map3.forEach((key,value)->map5.merge(key,value,(v1,v2)->v2-v1));
System.out.println("原始数据集1: "+map1);
System.out.println("原始数据集2: "+map2);
System.out.println("原始数据集3: "+map3);
System.out.println("存放相加value值的数据集Map: "+map5);
}