The literals should be first in String comparisons

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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);
    }
}