java.lang.String Rules

These rules deal with different problems that can occur with String manipulation.

AvoidDuplicateLiterals

Code containing duplicate String literals can usually be improved by declaring the String as a constant field.

This rule is defined by the following Java class: net.sourceforge.pmd.rules.AvoidDuplicateLiteralsRule

Here's an example of code that would trigger this rule:

			

public class Foo {
 private void bar() {
    buz("Howdy");
    buz("Howdy");
    buz("Howdy");
    buz("Howdy");
 }
 private void buz(String x) {}
}

StringInstantiation

Avoid instantiating String objects; this is usually unnecessary.

This rule is defined by the following XPath expression:

                   
    //AllocationExpression[ClassOrInterfaceType/@Image='String'][count(.//Expression) < 2][not(ArrayDimsAndInits)]

Here's an example of code that would trigger this rule:

			

public class Foo {
 private String bar = new String("bar"); // just do a String bar = "bar";
}

StringToString

Avoid calling toString() on String objects; this is unnecessary

This rule is defined by the following Java class: net.sourceforge.pmd.rules.StringToStringRule

Here's an example of code that would trigger this rule:

			

public class Foo {
 private String baz() {
  String bar = "howdy";
  return bar.toString();
 }
}

AvoidConcatenatingNonLiteralsInStringBuffer

Avoid concatenating non literals in a StringBuffer constructor or append().

This rule is defined by the following Java class: net.sourceforge.pmd.rules.AvoidConcatenatingNonLiteralsInStringBuffer

Here's an example of code that would trigger this rule:

			


// Avoid this 
StringBuffer sb=new
StringBuffer("AAAAAAAAAA"+System.getProperty("java.io.tmpdir"));

// use instead something like this
StringBuffer sb = new StringBuffer("AAAAAAAAAA");
sb.append(System.getProperty("java.io.tmpdir"));