# Use StringBuilder::append

# Properties

# 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.

# Requirement & Tags

# 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 + "";