Understanding the Differences Between a.equals(b) and Objects.equals(a, b) in Java

I always thought this method was introduced in Java 8, but discovered it actually dates back to Java 1.7, so I examined the source code. This article summarizes the differences between a.equals(b) and Objects.equals(a, b) and provides a brief source‑code analysis.

1. When the value is null

1. a.equals(b) – if a is null , a NullPointerException is thrown.

2. a.equals(b) – if a is not null but b is null , the method returns false .

3. Objects.equals(a, b) – returns true when both a and b are null ; returns false when exactly one of them is null . No NullPointerException is thrown.

null.equals("abc")    → throws NullPointerException
"abc".equals(null)    → returns false
null.equals(null)      → throws NullPointerException

Objects.equals(null, "abc") → returns false
Objects.equals("abc", null) → returns false
Objects.equals(null, null)   → returns true

2. When the value is an empty string

1. If both a and b are empty strings ( "" ), a.equals(b) returns true ; otherwise it returns false .

2. In this situation Objects.equals behaves identically to a.equals(b) .

"abc".equals("") → returns false
"".equals("abc") → returns false
"".equals("")    → returns true

Objects.equals("abc", "") → returns false
Objects.equals("", "abc") → returns false
Objects.equals("", "")    → returns true

3. Source‑code analysis

1. Source

public final class Objects {
    private Objects() {
        throw new AssertionError("No java.util.Objects instances for you!");
    }

    /**
     * Returns true if the arguments are equal to each other and false otherwise.
     * If both arguments are null, true is returned; if exactly one argument is null,
     * false is returned. Otherwise, equality is determined by using the
     * Object#equals method of the first argument.
     */
    public static boolean equals(Object a, Object b) {
        return (a == b) || (a != null && a.equals(b));
    }
}

2. Explanation

The method first checks whether the two references are identical ( a == b ). If they are, it returns true immediately.

If the references differ, the expression (a != null && a.equals(b)) is evaluated. It ensures that a is not null before invoking a.equals(b) , thereby avoiding a NullPointerException .

Consequently, when both arguments are null the first condition ( a == b ) is true. When they are different non‑null objects, the method relies on the logical equality defined by a.equals(b) .

4. Difference between a == b and a.equals(b)

If a and b are objects, a == b compares their references; it returns true only when both references point to the exact same object in memory.

In contrast, a.equals(b) performs a logical comparison of the objects' contents. It returns true when the objects are considered equal according to the class's overridden equals method, which may involve comparing fields rather than references.

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