Let's assume that we have some Map structere like below:
Map<Type, Map<String, String>> outterMap = new HashMap<>();
Map<String, String> innerMap1 = new HashMap<>();
innerMap1.put("1", "test1");
innerMap1.put("2", "test2");
innerMap1.put("3", "test3");
innerMap1.put("4", "test4");
Map<String, String> innerMap2 = new HashMap<>();
innerMap2.put("5", "test5");
innerMap2.put("6", "test6");
innerMap2.put("3", "test7");
outterMap.put(Type.TEXT, innerMap1);
outterMap.put(Type.INTEGER, innerMap2);
and we would like to print all values from innerMap with assigned Type enum. With foreach loop it would look like this:
for (Type type : outterMap.keySet()) {
for (String value : outterMap.get(type).values()) {
if(type.equals(Type.TEXT)) {
System.out.println("TEXT: " + value);
}else if(type.equals(Type.INTEGER)) {
System.out.println("INTEGER: " + value);
}
}
}
So the output on console would looks like this:
TEXT: test1
TEXT: test2
TEXT: test3
TEXT: test4
INTEGER: test7
INTEGER: test5
INTEGER: test6
Is there any option to write it with help of the streams. I was able to use stream with lambda, and it looks like this:
outterMap.keySet().stream().forEach(type -> {
outterMap.get(type)
.values()
.stream()
.forEach(value -> {
if(type.equals(Type.TEXT)) {
System.out.println("TEXT: " + value);
} else if (type.equals(Type.INTEGER)) {
System.out.println("INTEGER: " + value);
}
});
});
Probably this:
outterMap.keySet()
.stream()
.flatMap(x -> outterMap.getOrDefault(x, Collections.emptyMap())
.values()
.stream()
.map(y -> new SimpleEntry<>(x, y)))
.forEachOrdered(entry -> {
System.out.println(entry.getKey() + " " + entry.getValue());
});
But this is by far less readable than what you have.
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