Hi Michael,
If in your code you "know" that a particular key must be present, then
why aren't you using .get(key) in that place instead of
.computeIfAbsent() and trying to rely on it being a non-modifying operation?
Note that in some Map implementations (WeakHashMap for example) event
.get(key) may be an (internal structure) modifying operation.
Regards, Peter
On 11/20/18 10:41 AM, Michael Rasmussen wrote:
A quick snippet of code that shows this, by reflecting into the Map to get the
table field, and see that it changes:
/* --- snip --- */
package com.test;
import java.lang.reflect.Field;
import java.util.HashMap;
import java.util.function.Function;
public class Test {
public static void main(String[] args) throws Exception {
HashMap<Integer, Integer> map = new HashMap<>();
for (int i = 0; i < 13; i++) {
map.computeIfAbsent(i, Function.identity());
}
Field table = HashMap.class.getDeclaredField("table");
table.setAccessible(true);
System.out.println(map.containsKey(1));
System.out.println(table.get(map));
map.computeIfAbsent(1, Function.identity());
System.out.println(table.get(map));
}
}
/* --- snap --- */
true
[Ljava.util.HashMap$Node;@4cb2c100
[Ljava.util.HashMap$Node;@6fb554cc
/* --- snude --- */
