com.qulice.checkstyle.StringLiteralsConcatenationCheck Maven / Gradle / Ivy
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package com.qulice.checkstyle;
import com.puppycrawl.tools.checkstyle.api.AbstractCheck;
import com.puppycrawl.tools.checkstyle.api.DetailAST;
import com.puppycrawl.tools.checkstyle.api.TokenTypes;
import java.util.LinkedList;
import java.util.List;
/**
* Checks for not using concatenation of string literals in any form.
*
* The following constructs are prohibited:
*
*
* String a = "done in " + time + " seconds";
* System.out.println("File not found: " + file);
* x += "done";
*
*
* You should avoid string concatenation at all cost. Why? There are two
* reasons: readability of the code and translateability. First of all it's
* difficult to understand how the text will look after concatenation,
* especially if the text is long and there are more than a few {@code +}
* operators. Second, you won't be able to translate your text to other
* languages later, if you don't have solid string literals.
*
*
There are two alternatives to concatenation: {@link StringBuilder}
* and {@link String#format(String,Object[])}.
*
* @since 0.3
*/
public final class StringLiteralsConcatenationCheck extends AbstractCheck {
@Override
public int[] getDefaultTokens() {
return new int[] {TokenTypes.OBJBLOCK};
}
@Override
public int[] getAcceptableTokens() {
return this.getDefaultTokens();
}
@Override
public int[] getRequiredTokens() {
return this.getDefaultTokens();
}
@Override
public void visitToken(final DetailAST ast) {
final List pluses = this.findChildAstsOfType(
ast,
TokenTypes.PLUS,
TokenTypes.PLUS_ASSIGN
);
for (final DetailAST plus : pluses) {
if (!this.findChildAstsOfType(
plus,
TokenTypes.STRING_LITERAL
).isEmpty()) {
this.log(plus, "Concatenation of string literals prohibited");
}
}
}
/**
* Recursively traverse the tree and return all ASTs subtrees
* matching any type from types.
* @param tree AST to traverse.
* @param types Token types to match against.
* @return All ASTs subtrees with token types matching any from
* types.
* @see TokenTypes
*/
private List findChildAstsOfType(final DetailAST tree,
final int... types) {
final List children = new LinkedList<>();
DetailAST child = tree.getFirstChild();
while (child != null) {
if (StringLiteralsConcatenationCheck.isOfType(child, types)) {
children.add(child);
} else {
children.addAll(this.findChildAstsOfType(child, types));
}
child = child.getNextSibling();
}
return children;
}
/**
* Checks if this ast is of any type from types.
* @param ast AST to check.
* @param types Token types to match against.
* @return True if of type, false otherwise.
* @see TokenTypes
*/
private static boolean isOfType(final DetailAST ast, final int... types) {
boolean yes = false;
for (final int type : types) {
if (ast.getType() == type) {
yes = true;
break;
}
}
return yes;
}
}