src/main/java/org/plumelib/bcelutil/JvmUtil.java
public static @FieldDescriptor String primitiveTypeNameToFieldDescriptor(String primitiveName) {
    String result = primitiveClassesJvm.get(primitiveName);
    if (result == null) {
      throw new IllegalArgumentException("Not the name of a primitive type: " + primitiveName);
    }
    return result;
  }
public static @FieldDescriptor String primitiveTypeNameToFieldDescriptor(String primitiveName) {
    String result = primitiveClassesJvm.get(primitiveName);
    if (result == null) {
      throw new IllegalArgumentException("Not the name of a primitive type: " + primitiveName);
    }
    return result;
  }
Convert a primitive Java type name (e.g., "int", "double", etc.) to a field descriptor (e.g.,
"I", "D", etc.).

@param primitiveName name of the type, in Java format
@return name of the type, in field descriptor format
@throws IllegalArgumentException if primitiveName is not a valid primitive type name