refactor StreamReadConfig

Author: pjfanning

src/main/java/com/fasterxml/jackson/core/StreamReadConfig.java

@@ -9,17 +9,24 @@ public class StreamReadConfig {
 
     private static final int DEFAULT_MAX_NUM_LEN = 1000;
 
-    private int _maxNumLen = DEFAULT_MAX_NUM_LEN;
+    private int _maxNumLen;
+
+    public StreamReadConfig() {
+        _maxNumLen = DEFAULT_MAX_NUM_LEN;
+    }
+
+    private StreamReadConfig(int maxNumLen) {
+        _maxNumLen = maxNumLen;
+    }
 
     /**
      * Sets the maximum number length (in chars). The default is 1000 (since Jackson 2.14)
      * @param maxNumLen the maximum number length (in chars)
      * @return this config
      * @since 2.15
      */
-    public StreamReadConfig maxNumberLength(int maxNumLen) {
-        _maxNumLen = maxNumLen;
-        return this;
+    public StreamReadConfig withMaxNumberLength(int maxNumLen) {
+        return new StreamReadConfig(maxNumLen);
     }
 
     public int getMaxNumberLength() {

src/test/java/com/fasterxml/jackson/core/read/NumberOverflowTest.java

@@ -9,7 +9,7 @@ public class NumberOverflowTest
     extends com.fasterxml.jackson.core.BaseTest
 {
     private final JsonFactory FACTORY = JsonFactory.builder()
-            .streamReadConfig(new StreamReadConfig().maxNumberLength(1000000))
+            .streamReadConfig(new StreamReadConfig().withMaxNumberLength(1000000))
             .build();
 
     // NOTE: this should be long enough to trigger perf problems

src/test/java/com/fasterxml/jackson/core/read/NumberParsingTest.java

@@ -709,7 +709,7 @@ public void testLongNumbers2() throws Exception
         }
         final String DOC = input.toString();
         JsonFactory f = JsonFactory.builder()
-                .streamReadConfig(new StreamReadConfig().maxNumberLength(10000))
+                .streamReadConfig(new StreamReadConfig().withMaxNumberLength(10000))
                 .build();
         _testIssue160LongNumbers(f, DOC, false);
         _testIssue160LongNumbers(f, DOC, true);