===== 5.8 Fields =====

Each field is described by a variable-length **field_info** structure. The format of this structure is: 

The items of the **field_info structure** are as follows: 

**token** 

The token item is the token assigned to this field. There are three scopes for field tokens: **final **static**** fields of primitive types (compile-time constants), all other **static** fields, and **instance** fields. 

If this field is a compile-time constant, the value of the token item is 0xFF. Compile-time constants are represented in export files, but are not assigned token values suitable for late binding. Instead Java Card Converters must replace bytecodes that reference **final static** fields with bytecodes that load the constant value of the field.<SUP>[4]</SUP> 

If this field is **static**, but is not a compile-time constant, the token item represents a **static** field token ([[4.3.7.3_Static Fields| Section 4.3.7.3, Static Fields]]). 

If this field is an instance field, the token item represents an instance field token ([[4.3.7.5_Instance Fields| Section 4.3.7.5, Instance Fields]]). 

**access_flags** 

The value of the **access_flags** item is a mask of modifiers used with fields. The **access_flags** modifiers are shown in the following table. 

Name 

Value 

Meaning 

Used By 

ACC_PUBLIC 

0x0001 

Is public; may be accessed from outside its package. 

Any field 

ACC_PROTECTED 

0x0004 

Is protected; may be accessed within subclasses. 

Class field 

Instance field 

ACC_STATIC 

0x0008 

Is static. 

Class field 

Interface field 

ACC_FINAL 

0x0010 

Is final; no further overriding or assignment after initialization. 

Any field 

Field access and modifier flags are defined in the same way and with the same restrictions as described in The Java Virtual Machine Specification. 

Since all fields represented in an export file are either public or protected, exactly one of the **ACC_PUBLIC** or **ACC_PROTECTED** flag must be set. 

The Java Card virtual machine reserves all other flag values. Their values must be zero. 

**name_index** 

The value of the **name_index** item must be a valid index into the ****constant_pool**** table. The ****constant_pool**** entry at that index must be a **CONSTANT_Utf8_info** ([[5.6.4_CONSTANT_Utf8| Section 5.6.4, CONSTANT_Utf8]]) structure representing a valid Java field name stored as a simple (not fully qualified) name, that is, as a Java identifier. 

**descriptor_index** 

The value of the **descriptor_index** item must be a valid index into the ****constant_pool**** table. The ****constant_pool**** entry at that index must be a **CONSTANT_Utf8_info** ([[5.6.4_CONSTANT_Utf8| Section 5.6.4, CONSTANT_Utf8]]) structure representing a valid Java field descriptor. 

Representation of a field descriptor in an **export** file is the same as in a Java class file. See the specification described in The Java Virtual Machine Specification (&#167;4.3.2). 

If this field is a reference-type, the class referenced must be a public class. 

**attributes_count** 

The value of the ****attributes_count**** item indicates the number of additional attributes of this field. The only **field_info** attribute currently defined is the **ConstantValue** attribute ([[5.**1****0**.**1**_**ConstantValue** Attribute| Section 5.**1****0**.**1**, **ConstantValue** Attribute]]). For static final fields of primitive types, the value must be **1**; that is, when both the **ACC_STATIC** and **ACC_FINAL** bits in the **flags** item are set an attribute must be present. For all other fields the value of the ****attributes_count**** item must be **0**. 

**attributes[]** 

The only attribute defined for the attributes table of a **field_info** structure by this specification is the ConstantValue attribute ([[5.10.1_ConstantValue Attribute| Section 5.10.1, ConstantValue Attribute]]). This must be defined for static final fields of primitive types (**boolean**, **byte**, **short**, and **int**).