Update class constructors

Author: wyuinche

README.md

@@ -35,7 +35,11 @@ And this project includes below external libraries.
 * bitcoinj core v0.15.10
 * web3j core v4.8.7
 
-Download and use 'ecdsa-keygen-java-1.1' in 'release' tab or [here](release/).
+Download and use 'ecdsa-keygen-java-1.3.jar' in 'release' tab or [here](release/).
+
+```sh
+implementation files('./ecdsa-keygen-java-1.3.jar')
+```
 
 ## BTCKeyPair
 

lib/src/main/java/com/wuin/ecdsakeyj/BTCKeyPair.java

@@ -21,39 +21,56 @@
 public class BTCKeyPair extends ECDSAKeyPair {
     private ECKey keypair;
 
-    public BTCKeyPair() {
+    private BTCKeyPair() {
         String _priv = createPrivateKey();
         if (_priv != null) {
             this.priv = _priv;
         }
         createPublicKey();
     }
 
-    public BTCKeyPair(String priv, Boolean useSeed) {
-        if (useSeed) {
-            byte[] sh = Util.sha3(priv);
-            byte[] shb = Base58.encode(sh).getBytes();
-            shb = Arrays.copyOfRange(shb, 0, shb.length - 4);
-
-            BigInteger k = new BigInteger(shb);
-            BigInteger n = new BigInteger("115792089237316195423570985008687907852837564279074904382605163141518161494336");
-
-            k = k.mod(n);
-            k = k.add(new BigInteger("1"));
-            String key = Util.bytesToHexString(k.toByteArray());
-            
-            try {
-                String _priv = encodeKey(key);
-                this.priv = _priv;
-            } catch (Exception e) {
-                Util.raiseError("Fail to generate BTC Keypair from seed.");
-            }
-        } else {
-            this.priv = priv;
+    private BTCKeyPair(String priv) {
+        this.priv = priv;
+        createPublicKey();
+    }
+
+    private BTCKeyPair(byte[] seed) {
+        byte[] shb = Base58.encode(seed).getBytes();
+        shb = Arrays.copyOfRange(shb, 0, shb.length - 4);
+
+        BigInteger k = new BigInteger(shb);
+        BigInteger n = new BigInteger("115792089237316195423570985008687907852837564279074904382605163141518161494336");
+
+        k = k.mod(n);
+        k = k.add(new BigInteger("1"));
+        String key = Util.bytesToHexString(k.toByteArray());
+
+        try {
+            String _priv = encodeKey(key);
+            this.priv = _priv;
+        } catch (Exception e) {
+            Util.raiseError("Fail to generate BTC Keypair from seed.");
         }
         createPublicKey();
     }
 
+    public static BTCKeyPair create() {
+        return new BTCKeyPair();
+    }
+
+    public static BTCKeyPair fromPrivateKey(String priv) {
+        return new BTCKeyPair(priv);
+    }
+
+    public static BTCKeyPair fromSeed(String seed) {
+        byte[] sh = Util.sha3(seed);
+        return new BTCKeyPair(sh);
+    }
+
+    public static BTCKeyPair fromSeed(byte[] seed) {
+        return new BTCKeyPair(seed);
+    }
+
     private String createPrivateKey() {
         try {
             ECKey keypair = new ECKey();

lib/src/main/java/com/wuin/ecdsakeyj/ETHKeyPair.java

@@ -22,19 +22,27 @@
 public class ETHKeyPair extends ECDSAKeyPair {
     private ECKeyPair keypair;
 
-    public ETHKeyPair() {
+    private ETHKeyPair() {
         String _priv = createPrivateKey();
         if(_priv != null) {
             this.priv = _priv;
         }
         createPublicKey();
     }    
 
-    public ETHKeyPair(String priv) {
+    private ETHKeyPair(String priv) {
         super(priv);
         createPublicKey();
     }
 
+    public static ETHKeyPair create() {
+        return new ETHKeyPair();
+    }
+
+    public static ETHKeyPair fromPrivateKey(String priv) {
+        return new ETHKeyPair(priv);
+    }
+
     private String createPrivateKey() {
         try {
             return new ECKey().getPrivateKeyAsHex();