How do I check if two strings are equal in Java when either one of the strings can be a null?

Question

I have two strings ...

String s1 = /* any string, could be null */;
String s2 = /* any string, could be null */;

I need to know if they are equal.

I can't do s1.equals(s2) because NullPointer if s1 == null.

Is this the best way to check if they are equal?

public boolean stringsAreEqual(String s1, String s2) {
    boolean bEqual = false;
    if ((s1 == null) && (s2 == null)) {
        bEqual = true;
    } else if ((s1 != null) && s1.equals(s2)) {
        bEqual = true;
    } else if ((s2 != null) && s2.equals(s1)) {
        bEqual = true;
    }  
    return bEqual;
}

@Swati Don't recommend third party libs please. – Anish B. Sep 18 '20 at 04:37 — Anish B., Sep 18 '20 at 04:37

score 10 · Accepted Answer · answered Sep 18 '20 at 04:33

You do not need to create a new method for that. You can use java.util.Objects#equals(Object a, Object b) from the Java standard library. Below is the definition as on JDK.

public static boolean equals(Object a, Object b) {
    return (a == b) || (a != null && a.equals(b));
}

score 1 · Answer 2 · answered Sep 18 '20 at 04:34

1

You can compare strings like this. This is what Java internal code uses.

public boolean stringsAreEqual(String s1, String s2) {
    return (s1 == null ? s2 == null : s1.equals(s2));
}

answered Sep 18 '20 at 04:34

Derek Wang

10,098
4
18
39

score 1 · Answer 3 · answered Sep 18 '20 at 04:34

1

A==null ? B==null : A.equals(B)

answered Sep 18 '20 at 04:34

ddyer

1,792
19
26

Please add more information or explanation to justify the answer. – Devang Padhiyar Sep 18 '20 at 05:09
Less "readable" than I normally would write, but this is a nice concise solution. :) – AvaTaylor Sep 18 '20 at 05:13

score 1 · Answer 4 · answered Sep 18 '20 at 04:35

It seems like you could first make the method static, and second test if s1 is null, if it is test s2 for null. Otherwise compare s1 and s2. Like,

public static boolean stringsAreEqual(String s1, String s2) {
    if (s1 == null) {
        return s2 == null;
    }
    return s1.equals(s2);
}

How do I check if two strings are equal in Java when either one of the strings can be a null?

4 Answers4