Refactor Java API (#806)

sherpa-onnx/java-api/src/com/k2fsa/sherpa/onnx/OnlineTransducerModelConfig.java

@@ -1,6 +1,5 @@
-/*
- * // Copyright 2022-2023 by zhaoming
- */
+// Copyright 2022-2023 by zhaoming
+// Copyright 2024 Xiaomi Corporation
 
 package com.k2fsa.sherpa.onnx;
 
@@ -9,10 +8,14 @@ public class OnlineTransducerModelConfig {
     private final String decoder;
     private final String joiner;
 
-    public OnlineTransducerModelConfig(String encoder, String decoder, String joiner) {
-        this.encoder = encoder;
-        this.decoder = decoder;
-        this.joiner = joiner;
+    private OnlineTransducerModelConfig(Builder builder) {
+        this.encoder = builder.encoder;
+        this.decoder = builder.decoder;
+        this.joiner = builder.joiner;
+    }
+
+    public static Builder builder() {
+        return new Builder();
     }
 
     public String getEncoder() {
@@ -26,4 +29,29 @@ public class OnlineTransducerModelConfig {
     public String getJoiner() {
         return joiner;
     }
+
+    public static class Builder {
+        private String encoder = "";
+        private String decoder = "";
+        private String joiner = "";
+
+        public OnlineTransducerModelConfig build() {
+            return new OnlineTransducerModelConfig(this);
+        }
+
+        public Builder setEncoder(String encoder) {
+            this.encoder = encoder;
+            return this;
+        }
+
+        public Builder setDecoder(String decoder) {
+            this.decoder = decoder;
+            return this;
+        }
+
+        public Builder setJoiner(String joiner) {
+            this.joiner = joiner;
+            return this;
+        }
+    }
 }