[bitpay#420] Add Java 25 support

Author: swlodarski-sumoheavy

.github/workflows/build.yml

@@ -8,11 +8,11 @@ jobs:
 
     strategy:
       matrix:
-        java-version: [8, 11, 17, 21, 23]
+        java-version: [8, 11, 17, 21, 23, 25]
 
     steps:
-      - uses: actions/checkout@v4
-      - uses: actions/setup-java@v4
+      - uses: actions/checkout@v6
+      - uses: actions/setup-java@v5
         with:
           java-version: ${{ matrix.java-version }}
           distribution: 'corretto'

.github/workflows/documentation.yml

@@ -14,8 +14,8 @@ jobs:
     runs-on: ubuntu-latest
 
     steps:
-      - uses: actions/checkout@v4
-      - uses: actions/setup-java@v4
+      - uses: actions/checkout@v6
+      - uses: actions/setup-java@v5
         with:
           java-version: 8
           distribution: 'corretto'
@@ -31,4 +31,4 @@ jobs:
           git config user.email ""
           git add docs/
           git commit -m "Update javadoc" || echo "No changes to commit"
-          git push
+          git push

src/main/java/com/bitpay/sdk/util/KeyUtils.java

@@ -48,6 +48,11 @@ public KeyUtils() {
     public static boolean privateKeyExists(String privateKeyFile) {
         PrivateKeyFile = privateKeyFile;
 
+        // if the private key file is null or empty, return false
+        if (privateKeyFile == null || privateKeyFile.isEmpty()) {
+            return false;
+        }
+
         return new File(privateKeyFile).exists();
     }