Add abstractions for converting between SCVal and native types.

src/main/java/org/stellar/sdk/Address.java

@@ -1,6 +1,6 @@
 package org.stellar.sdk;
 
-import com.google.common.base.Objects;
+import lombok.EqualsAndHashCode;
 import org.stellar.sdk.xdr.Hash;
 import org.stellar.sdk.xdr.SCAddress;
 import org.stellar.sdk.xdr.SCVal;
@@ -10,8 +10,9 @@
  * Represents a single address in the Stellar network. An address can represent an account or a
  * contract.
  */
+@EqualsAndHashCode
 public class Address {
-
+  private static final SCValType TYPE = SCValType.SCV_ADDRESS;
   private final byte[] key;
 
   private final AddressType type;
@@ -77,8 +78,10 @@ public static Address fromSCAddress(SCAddress scAddress) {
    * @return a new {@link Address} object from the given XDR object
    */
   public static Address fromSCVal(SCVal scVal) {
-    if (!SCValType.SCV_ADDRESS.equals(scVal.getDiscriminant())) {
-      throw new IllegalArgumentException("SCVal is not of type SCV_ADDRESS");
+    if (!TYPE.equals(scVal.getDiscriminant())) {
+      throw new IllegalArgumentException(
+          String.format(
+              "invalid scVal type, expected %s, but got %s", TYPE, scVal.getDiscriminant()));
     }
     return Address.fromSCAddress(scVal.getAddress());
   }
@@ -112,7 +115,7 @@ public SCAddress toSCAddress() {
    */
   public SCVal toSCVal() {
     SCVal scVal = new SCVal();
-    scVal.setDiscriminant(SCValType.SCV_ADDRESS);
+    scVal.setDiscriminant(TYPE);
     scVal.setAddress(this.toSCAddress());
     return scVal;
   }
@@ -131,25 +134,10 @@ public byte[] getBytes() {
    *
    * @return the type of this address.
    */
-  public AddressType getType() {
+  public AddressType getAddressType() {
     return type;
   }
 
-  @Override
-  public int hashCode() {
-    return Objects.hashCode(this.key, this.type);
-  }
-
-  @Override
-  public boolean equals(Object object) {
-    if (!(object instanceof Address)) {
-      return false;
-    }
-
-    Address other = (Address) object;
-    return Objects.equal(this.key, other.key) && Objects.equal(this.type, other.type);
-  }
-
   @Override
   public String toString() {
     switch (this.type) {

src/main/java/org/stellar/sdk/InvokeHostFunctionOperation.java

@@ -36,6 +36,7 @@
  *
  * @see <a href="https://developers.stellar.org/docs/fundamentals-and-concepts/list-of-operations"
  *     target="_blank">List of Operations</a>
+ * @see org.stellar.sdk.scval.Scv
  */
 @EqualsAndHashCode(callSuper = true)
 @SuperBuilder(toBuilder = true)
@@ -225,6 +226,7 @@ public static InvokeHostFunctionOperation fromXdr(InvokeHostFunctionOp op) {
    * parameter preset, so that you can conveniently build an {@link InvokeHostFunctionOperation} to
    * invoke a contract function.
    *
+   * @see org.stellar.sdk.scval.Scv
    * @see <a
    *     href="https://soroban.stellar.org/docs/fundamentals-and-concepts/interacting-with-contracts"
    *     target="_blank">Interacting with Contracts</a>
@@ -236,7 +238,7 @@ public static InvokeHostFunctionOperation fromXdr(InvokeHostFunctionOp op) {
   public static InvokeHostFunctionOperationBuilder<?, ?> invokeContractFunctionOperationBuilder(
       String contractId, String functionName, @Nullable Collection<SCVal> parameters) {
     Address address = new Address(contractId);
-    if (address.getType() != Address.AddressType.CONTRACT) {
+    if (address.getAddressType() != Address.AddressType.CONTRACT) {
       throw new IllegalArgumentException("\"contractId\" must be a contract address");
     }
     SCVal contractIdScVal = address.toSCVal();

src/main/java/org/stellar/sdk/Util.java

@@ -1,5 +1,6 @@
 package org.stellar.sdk;
 
+import java.math.BigInteger;
 import java.security.MessageDigest;
 import java.security.NoSuchAlgorithmException;
 import java.util.Arrays;
@@ -99,4 +100,22 @@ public static AssetTypeCreditAlphaNum assertNonNativeAsset(Asset asset) {
     }
     throw new IllegalArgumentException("native assets are not supported");
   }
+
+  /**
+   * Returns an 8 byte array representation of a BigInteger value.
+   *
+   * @param value BigInteger value to convert to byte array
+   * @return byte array
+   */
+  public static byte[] getBytes(BigInteger value) {
+    byte[] bytes = value.toByteArray();
+    if (bytes.length < 8) {
+      byte[] temp = new byte[8];
+      System.arraycopy(bytes, 0, temp, 8 - bytes.length, bytes.length);
+      bytes = temp;
+    } else if (bytes.length > 8) {
+      bytes = Arrays.copyOfRange(bytes, bytes.length - 8, bytes.length);
+    }
+    return bytes;
+  }
 }