The literals should be first in String comparisons

Docs > Code Analysis > Static Analysis Rules > The literals should be first in String comparisons

This page is not yet available in Spanish. We are working on its translation.
If you have any questions or feedback about our current translation project, feel free to reach out to us!

Metadata

ID: java-best-practices/literals-first-in-comparison

Language: Java

Severity: Warning

Category: Best Practices

Description

One should always prioritize using a string literal as the first arguments in any string comparison. This approach serves as a preventive measure against NullPointerExceptions because when the second argument is null, instead of encountering an exception, the comparisons will simply yield false results.

Non-Compliant Code Examples

class Foo {
    boolean bar(String x) {
        return x.equals("42"); // should be "42".equals(x)
    }
    boolean bar(String x) {
        return x.equalsIgnoreCase("42"); // should be "42".equalsIgnoreCase(x)
    }
    boolean bar(String x) {
        return (x.compareTo("bar") > 0); // should be: "bar".compareTo(x) < 0
    }
    boolean bar(String x) {
        return (x.compareToIgnoreCase("bar") > 0); // should be: "bar".compareToIgnoreCase(x) < 0
    }
    boolean baz(String x) {
        return x.contentEquals("baz"); // should be "baz".contentEquals(x)
    }
}

Compliant Code Examples

class Foo {
    boolean bar(String x) {
        return "42".equals(x);
    }
    boolean bar(String x) {
        return "42".equalsIgnoreCase(x);
    }
    boolean bar(String x) {
        return "bar".compareTo(x) < 0;
    }
    boolean bar(String x) {
        return "bar".compareToIgnoreCase(x) < 0;
    }
    boolean baz(String x) {
        return "baz".contentEquals(x);
    }
}