fix: allow extendTo to be 0 in ExtendFootprintTTLOperation

CHANGELOG.md

@@ -2,6 +2,9 @@
 
 ## Pending
 
+### Update
+- fix: allow `extendTo` to be 0 in `ExtendFootprintTTLOperation`. ([#810](https://github.com/lightsail-network/java-stellar-sdk/issues/810))
+
 ## 4.0.0
 
 This release contains everything from 4.0.0-beta0, plus the changes made since. Below is the changelog since 3.1.0.

src/main/java/org/stellar/sdk/operations/ExtendFootprintTTLOperation.java

@@ -62,7 +62,9 @@ public abstract static class ExtendFootprintTTLOperationBuilder<
           C extends ExtendFootprintTTLOperation, B extends ExtendFootprintTTLOperationBuilder<C, B>>
       extends OperationBuilder<C, B> {
     public B extendTo(Long extendTo) {
-      if (extendTo <= 0 || extendTo > 0xFFFFFFFFL) {
+      // `extendTo` can be 0, see
+      // https://github.com/lightsail-network/java-stellar-sdk/issues/810
+      if (extendTo < 0 || extendTo > 0xFFFFFFFFL) {
         throw new IllegalArgumentException("extendTo isn't a ledger quantity (uint32)");
       }
       this.extendTo = extendTo;

src/test/java/org/stellar/sdk/operations/ExtendFootprintTTLOperationTest.java

@@ -68,6 +68,12 @@ public void testNotEqualsSource() {
     Assert.assertNotEquals(operation1, operation2);
   }
 
+  @Test
+  public void testLedgersToExpireIsZero() {
+    ExtendFootprintTTLOperation op = ExtendFootprintTTLOperation.builder().extendTo(0L).build();
+    assertEquals(Long.valueOf(0), op.getExtendTo());
+  }
+
   @Test
   public void testLedgersToExpireIsInvalidThrowsLessThanZero() {
     try {