Fix potential IllegalStateException in Limit.

Fixes GH-3023.

Author: odrotbohm

Diff for: src/main/java/org/springframework/data/domain/Limit.java

@@ -17,7 +17,7 @@
 
 import org.springframework.data.domain.Limit.Limited;
 import org.springframework.data.domain.Limit.Unlimited;
-import org.springframework.util.ClassUtils;
+import org.springframework.lang.Nullable;
 
 /**
  * {@link Limit} represents the maximum value up to which an operation should continue processing. It may be used for
@@ -94,14 +94,17 @@ public boolean equals(Object obj) {
 			if (obj == null) {
 				return false;
 			}
-			if (!ClassUtils.isAssignable(Limit.class, obj.getClass())) {
+
+			if (!(obj instanceof Limit that)) {
 				return false;
 			}
-			Limit that = (Limit) obj;
-			if (this.isUnlimited() && that.isUnlimited()) {
-				return true;
+
+			if (this.isUnlimited() ^ that.isUnlimited()) {
+				return false;
 			}
-			return max() == that.max();
+
+			return this.isUnlimited() && that.isUnlimited()
+					|| max() == that.max();
 		}
 
 		@Override

Diff for: src/test/java/org/springframework/data/domain/LimitUnitTests.java

@@ -55,4 +55,15 @@ void isUnlimitedReturnsFalseIfLimited(int value) {
 	void unlimitedErrorsOnMax() {
 		assertThatExceptionOfType(IllegalStateException.class).isThrownBy(() -> Limit.unlimited().max());
 	}
+
+	@Test // GH-3023
+	void equalsProperly() {
+
+		Limit unlimited = Limit.unlimited();
+		Limit limited = Limit.of(5);
+
+		assertThat(limited.equals(unlimited)).isFalse();
+		assertThat(unlimited.equals(limited)).isFalse();
+		assertThat(unlimited.equals(unlimited)).isTrue();
+	}
 }