Update map using findAll and each in groovy

Question

I would like to update values in map in Groovy filling certain criteria. Here is my code:

def m = [:]
m['a'] = 1
m['b'] = 2
m['d'] = 3
m.findAll { it.value > 1}.each { 
it.value = 4
}
println m

But the result is following:

[a:1, b:2, d:3]

Is there any way to do it using both findAll and each? Or I must use

m.each {if (it.value>1) it.value=4}

Answer 1

The root cause is findAll returns a new Map instance.

So you could try:

newMap = m.findAll { it.value > 1}.each { 
    it.value = 4
}
println m      //No change
println newMap //This is what you need!

output is

[a:1, b:2, d:3] 
[b:4, d:4]

Answer 2

In each case, the values you are iterating with the each are map entries with a pointer to key and value. When you set it.value you are not replacing what is in the map. You are only updating the pointer in the map entry. To actually set the value, you will need to do the following:

m.findAll { it.value > 1 }.each { m[it.key] = 4 }