Create java-howto.md

Author: taowen

java-howto.md

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+---
+layout: default
+title: How-to
+---
+
+# Simple Object binding
+
+bind the json document 
+
+```json
+{"field1":100,"field2":101}
+```
+
+to the class
+
+```java
+public static class TestObject {
+    public int field1;
+    public int field2;
+}
+```
+
+## iterator + switch case
+
+```java
+TestObject obj = new TestObject();
+for (String field = iter.readObject(); field != null; field = iter.readObject()) {
+    switch (field) {
+        case "field1":
+            obj.field1 = iter.readInt();
+            continue;
+        case "field2":
+            obj.field2 = iter.readInt();
+            continue;
+        default:
+            iter.skip();
+    }
+}
+return obj;
+```
+
+## iterator + if/else
+
+```java
+TestObject obj = new TestObject();
+for (String field = iter.readObject(); field != null; field = iter.readObject()) {
+    if (field.equals("field1")) {
+        obj.field1 = iter.readInt();
+        continue;
+    }
+    if (field.equals("field2")) {
+        obj.field2 = iter.readInt();
+        continue;
+    }
+    iter.skip();
+}
+return obj;
+```
+
+## iterator + if/else + string.intern
+
+```java
+TestObject obj = new TestObject();
+for (String field = iter.readObject(); field != null; field = iter.readObject()) {
+    field = field.intern();
+    if (field == "field1") {
+        obj.field1 = iter.readInt();
+        continue;
+    }
+    if (field == "field2") {
+        obj.field2 = iter.readInt();
+        continue;
+    }
+    iter.skip();
+}
+return obj;
+```
+
+## performance
+
+| style | ops/s |
+| --- | --- | 
+| iterator + switch case | 10161124.096 ±  86811.453  ops/s |
+| iterator if/else |  10566399.972 ± 219004.245  ops/s |
+| iterator if/else + string.intern | 4091671.061 ±  59660.899  ops/s |
+
+Do not use string.intern, it will not be faster. If/else might be slightly faster than switch/case, but swtich case is much more readable.