# Use StringBuilder::append
# Properties
| Property | Value |
|---|---|
| Rule ID | UseStringBuilderAppend |
| First seen in jSparrow version | 2.7.0 |
| Minimum Java version | 5 |
| Remediation cost | 2 min |
| Links | S1643 |
# Description
Replaces the infix operator + over String concatenations with at least three operands by StringBuilder::append. When possible, unwraps the parenthesized expressions.
# Benefits
Improves the performance of the String concatenations.
# Code Changes
# Concatenating strings in infix expressions
Pre
String value = "prefix" + "value" + "suffix";
Post
String value = new StringBuilder().append("prefix")
.append("value")
.append("suffix")
.toString();
# Resolving types of arithmetic expressions
Pre
String value = "prefix" + 2 * 3 + ("value" + 2 + 3) + (4 + 5) + "suffix";
Post
String value = new StringBuilder().append("prefix")
.append(2*3)
.append("value")
.append(2)
.append(3)
.append(4 + 5)
.append("suffix")
.toString();
# Resolving types of numeric literals
Pre
String value = 5 + " (five) = " + 3 + " (three) + " + 2 + " (two).";
Post
String value = new StringBuilder().append(5)
.append(" (five) = ")
.append(3)
.append(" (three) + ")
.append(2)
.append(" (two).")
.toString();
# Limitations
If at least two of the first operands of the expression are numeric additions then the expression is evaluated by Java as numeric expression rather than String expression. Therefore, the transformation is not performed. E.g.:
Pre
String value = 2 + 3 + "";
Automatic Application of This Rule
The automatic application of this rule is supported in the following jSparrow version:
# Tags
1
You & jSparrow
