# Replace put(..) with putIfAbsent(..)
# Description
If map.put(..) is wrapped with a condition verifying the existence of an element, one can use map.putIfAbsent(...) instead.
# Benefits
Makes the code more readable, by using Java 8 extensions of Map interface.
# Tags
# Code Changes
# Default
Pre
if (!map.containsKey(aKey)) {
map.put(aKey, aValue);
}
Post
map.putIfAbsent(aKey, aValue);
# No Block present
Pre
if (!map.containsKey(aKey))
map.put(aKey, aValue);
Post
map.putIfAbsent(aKey, aValue);
# Including Null-Checks
Pre
V v = map.get(key);
if (v == null) {
v = map.put(key, value);
}
return v;
Post
map.putIfAbsent(key, value);
return v;
# Bytecode JDK 1.8
Pre
public void original(Map<String, String> map, String newKey, String newValue) {
if(!map.containsKey(newKey)) {
map.put(newKey, newValue);
}
}
0 aload_1
1 aload_2
2 invokeinterface #2 <java/util/Map.containsKey> count 2
7 ifne 19 (+12)
10 aload_1
11 aload_2
12 aload_3
13 invokeinterface #3 <java/util/Map.put> count 3
18 pop
19 return
Post
public void transformed(Map<String, String> map, String newKey, String newValue) {
map.putIfAbsent(newKey, newValue);
}
0 aload_1
1 aload_2
2 aload_3
3 invokeinterface #4 <java/util/Map.putIfAbsent> count 3
8 pop
9 return
# Limitations
The rule can be applied if a map type is present, a call to map.put(..) is present, and that call is wrapped in an if-Statement.
Use a Java Refactoring Tool
No license required
You can review this refactoring on your code without a license by installing jSparrow to your Eclipse IDE. Install the plug-in from Eclipse IDE: Eclipse Marketplace.
System-wide Refactoring
Do you want to automate this refactoring (and many more) to your system-wide code? The automatic application of this system-wide refactoring can be unlocked by acquiring your jSparrow license.
# Properties
| Property | Value |
|---|---|
| Rule ID | PutIfAbsent |
| First seen in jSparrow version | 2.3.0 |
| Minimum Java version | 8 |
| Remediation cost | 2 min |