# Replace Concatenation with Infix-Operation
# Description
This rule replaces the concat() method on Strings with the + operator.
For example, s = s.concat("bar") becomes s = s + "bar". This improves readability and performance for
chained concatenations.
# Benefits
Applying this rule has slight performance benefits and arguably improves readability.
The Java compiler will convert the + operation to use a StringBuilder.
The more concatenations occur, the bigger the performance gain is.
# Tags
# Code Changes
# Base case
Pre
String s = "foo";
s = s.concat("bar");
Post
String s = "foo";
s = s + "bar";
# Chained concatenation expression
Pre
input.concat("abc").concat("cde").concat("fgh".concat("hij"));
Post
input + "abc" + "cde" + "fgh" + "hij";
# Nested concatenation expressions
Pre
input.concat(param.concat(param));
Post
input + param + param;
# Bytecode JDK 1.8
Pre
public void original() {
String value = "foo".concat("bar");
}
0 ldc #2 <foo>
2 ldc #3 <bar>
4 invokevirtual #4 <java/lang/String.concat>
7 astore_1
8 return
Post
public void transformed() {
String value = "foo" + "bar";
}
0 ldc #5 <foobar>
2 astore_1
3 return
🛠️ Auto-refactor Available
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# Properties
| Property | Value |
|---|---|
| Rule ID | StringConcatToPlus |
| First seen in jSparrow version | 1.0.0 |
| Minimum Java version | 1.1 |
| Remediation cost | 5 min |