Null Pointer from using Reflection in java [duplicate]

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• What is a NullPointerException, and how do I fix it? 12 answers

Here I have class and i want to write a testcase. Testcase also given below.But in the test case expectedPrefixArray.add(String.valueOf( field.get(CACHE_KEY_PREFIX.KeyPrefix.class))); return a nullpointer.What is the reason for this? Accessebility also set to true. Some help me please.......................

public enum CACHE_KEY_PREFIX {

SYMBOL_CACHE(new String[]{KeyPrefix.KEY_PREFIX_SYMBOL_CACHE_SRC_DEFAULT, KeyPrefix.KEY_PREFIX_SYMBOL_CACHE_SRC_RIC,
        KeyPrefix.KEY_PREFIX_SYMBOL_CACHE_SRC_ISIN}),
EXCHANGE_CACHE(new String[]{KeyPrefix.KEY_PREFIX_EXCHANGE_CACHE_TAG_DEFAULT, KeyPrefix.KEY_PREFIX_EXCHANGE_CACHE_TAG_207,
        KeyPrefix.KEY_PREFIX_EXCHANGE_CACHE_TAG_100, KeyPrefix.KEY_PREFIX_EXCHANGE_CACHE_TICK_SIZES}),
LOGIN_ID_MAPPINGS_CACHE(new String[]{KeyPrefix.KEY_PREFIX_LOGIN_CASH_ACNT_MAP, KeyPrefix.KEY_PREFIX_LOGIN_TRADING_MAP}),
U08_BENEFICIARY_ACCOUNT_CACHE(new String[]{KeyPrefix.KEY_PREFIX_BENEFICIARY_CACHE}),
CURRENCY_CACHE(new String[]{KeyPrefix.KEY_PREFIX_CURRENCY_STORE, KeyPrefix.KEY_PREFIX_DECIMAL_CURRENCY}),
U06_CASH_ACCOUNT_CACHE(new String[]{KeyPrefix.KEY_PREFIX_CASH_ACNT_TRANSACTION}),
U06_CASH_ACCOUNT_MASTER_DATA_CACHE(new String[]{KeyPrefix.KEY_PREFIX_CASH_ACNT_MASTER_DATA}),
MARKET_RESTRICTION_CACHE(new String[]{KeyPrefix.KEY_PREFIX_ALLOWED_TIF_BY_STATUS, KeyPrefix.KEY_PREFIX_ALLOWED_ACTION_BY_STATUS,
        KeyPrefix.KEY_PREFIX_ALLOWED_ORDER_TYPES}),
USER_ID_MAPPINGS_CACHE(new String[]{KeyPrefix.KEY_PREFIX_USERID_CASH_ACNT_MAP}),
ORD_CHANNEL_CACHE(new String[]{KeyPrefix.KEY_PREFIX_CHANNEL}),
MARGIN_SYMBOL_CACHE(new String[]{KeyPrefix.KEY_PREFIX_MARGIN_SYMBOL_MARGINABILITY, KeyPrefix.KEY_PREFIX_MARGIN_STOCK_CONCENTRATION}),
U07_TRADING_ACNT_CACHE(new String[]{KeyPrefix.KEY_PREFIX_TRD_ANCT_BY_NO, KeyPrefix.KEY_PREFIX_TRD_ANCT_BY_EXT_NO, KeyPrefix.KEY_PREFIX_TRD_ANCT_BY_ID}),
TRADING_MARKET_CACHE(new String[]{KeyPrefix.KEY_PREFIX_TRADNG_MRKT, KeyPrefix.KEY_PREFIX_CNN_ALIAS_TRADNG_MRKT,
        KeyPrefix.KEY_PREFIX_TRADNG_MRKT_EXG_BY_TAGS, KeyPrefix.KEY_PREFIX_TRADNG_MRKT_BY_TYPE, KeyPrefix.KEY_PREFIX_EXEBRK_TRADNG_MRKT,
        KeyPrefix.KEY_PREFIX_M29_MARKET_BY_EXG, KeyPrefix.KEY_PREFIX_M29_MARKET_BY_ALL}),
COMMISSION_GROUP_BY_CHANNEL_CACHE(new String[]{KeyPrefix.KEY_PREFIX_COMMISION_GRP_BY_CHANNEL_DLMTD}),
POWER_OF_ATTORNEY_CACHE(new String[]{KeyPrefix.KEY_PREFIX_POA}),
EXT_REF_MAP_CACHE(new String[]{KeyPrefix.KEY_PREFIX_EXT_REF_MAP_CACHE_RCLIORDID, KeyPrefix.KEY_PREFIX_EXT_REF_MAP_CACHE_EXGORDID}),
TRADING_HOLDING_MAPPING_CACHE(new String[]{KeyPrefix.KEY_PREFIX_CASH_TRADING_MAP, KeyPrefix.KEY_PREFIX_CASH_ACNT_TO_HOLDING_MAP}),
COMMISSION_SLABS_CACHE(new String[]{KeyPrefix.KEY_PREFIX_COMMISSION_GRP, KeyPrefix.KEY_PREFIX_EXEC_BROKER_COMMISSION_DLMTD, KeyPrefix.KEY_PREFIX_CUSTOMER_COMMISSION_DLMTD,
        KeyPrefix.KEY_PREFIX_COMMISSION_DISCOUNT_DLMTD}),
CHARGE_CACHE(new String[]{KeyPrefix.KEY_PREFIX_CHARGE}),
//Todo remove this
CASH_PRECISION_CACHE(new String[]{KeyPrefix.CACHE_KEY_CASH_PRECESSION});

public static class KeyPrefix {
    public static final String KEY_PREFIX_SYMBOL_CACHE_SRC_RIC = "RIC";
    public static final String KEY_PREFIX_SYMBOL_CACHE_SRC_ISIN = "ISIN";
    public static final String KEY_PREFIX_SYMBOL_CACHE_SRC_DEFAULT = "DEFAULT";
    public static final String KEY_PREFIX_EXCHANGE_CACHE_TAG_100 = "TAG_100";
    public static final String KEY_PREFIX_EXCHANGE_CACHE_TAG_207 = "TAG_207";
    public static final String KEY_PREFIX_EXCHANGE_CACHE_TAG_DEFAULT = "DEFAULT";
    public static final String KEY_PREFIX_EXCHANGE_CACHE_TICK_SIZES = "EXG_TICK";
    public static final String KEY_PREFIX_LOGIN_TRADING_MAP = "LTMAP";
    public static final String KEY_PREFIX_LOGIN_CASH_ACNT_MAP = "LCMAP";
    public static final String KEY_PREFIX_BENEFICIARY_CACHE = "U08BEN";
    public static final String KEY_PREFIX_CURRENCY_STORE = "CRSTR";
    public static final String KEY_PREFIX_DECIMAL_CURRENCY = "DCR";
    public static final String KEY_PREFIX_CASH_ACNT_TRANSACTION = "TXNCash";
    public static final String KEY_PREFIX_CASH_ACNT_MASTER_DATA = "MSTRCash";
    public static final String KEY_PREFIX_ALLOWED_TIF_BY_STATUS = "MKT_TIF";
    public static final String KEY_PREFIX_ALLOWED_ACTION_BY_STATUS = "MKT_STATUS";
    public static final String KEY_PREFIX_ALLOWED_ORDER_TYPES = "ORD_TYPES";
    public static final String KEY_PREFIX_USERID_CASH_ACNT_MAP = "LUCMAP";
    public static final String KEY_PREFIX_CHANNEL = "ORDCHNEL";
    public static final String KEY_PREFIX_MARGIN_SYMBOL_MARGINABILITY = "SYMBOL_MAR";
    public static final String KEY_PREFIX_MARGIN_STOCK_CONCENTRATION = "STOCK_CON";
    public static final String KEY_PREFIX_TRD_ANCT_BY_NO = "TRD_NO";
    public static final String KEY_PREFIX_TRD_ANCT_BY_EXT_NO = "TRD_NO_EXT";
    public static final String KEY_PREFIX_TRD_ANCT_BY_ID = "TRD_ID";
    public static final String KEY_PREFIX_TRADNG_MRKT = "TM";
    public static final String KEY_PREFIX_CNN_ALIAS_TRADNG_MRKT = "CATM";
    public static final String KEY_PREFIX_TRADNG_MRKT_EXG_BY_TAGS = "EXG_BY_TAGS_49_56";
    public static final String KEY_PREFIX_TRADNG_MRKT_BY_TYPE = "TYPE_TM";
    public static final String KEY_PREFIX_EXEBRK_TRADNG_MRKT = "EXTM";
    public static final String KEY_PREFIX_M29_MARKET_BY_EXG = "M29MKT_EXG";
    public static final String KEY_PREFIX_M29_MARKET_BY_ALL = "M29MKT_ALL";
    public static final String KEY_PREFIX_COMMISION_GRP_BY_CHANNEL_DLMTD = "CHCOM";
    public static final String KEY_PREFIX_POA = "POA";
    public static final String KEY_PREFIX_COMMISSION_GRP = "GRP";
    public static final String KEY_PREFIX_EXEC_BROKER_COMMISSION_DLMTD = "ECOM";
    public static final String KEY_PREFIX_CUSTOMER_COMMISSION_DLMTD = "CCOM";
    public static final String KEY_PREFIX_COMMISSION_DISCOUNT_DLMTD = "DCOM";
    public static final String KEY_PREFIX_EXT_REF_MAP_CACHE_RCLIORDID = "RCLIORDID";
    public static final String KEY_PREFIX_EXT_REF_MAP_CACHE_EXGORDID = "EXGORDID";
    public static final String KEY_PREFIX_CASH_TRADING_MAP = "CASH_TRADING";
    public static final String KEY_PREFIX_CASH_ACNT_TO_HOLDING_MAP = "CASH_ACC_HOLDINGS_MAP";

    public static final String CACHE_KEY_CASH_PRECESSION = "CASH_PRECESSION";
    public static final String KEY_PREFIX_CHARGE = "CHARGE";

}

public String[] prefixArray;
CACHE_KEY_PREFIX(String[] prefixArray) {
    this.prefixArray = prefixArray;
}

public static String KEY_SEPARATOR = "~";
public static String KEY_PREFIX_DEFAULT = "KEY_DEFAULT";




 @Test
  public void checkCachePrefixAvailableTest() throws Exception {
    List<String> expectedPrefixArray = new ArrayList<>();
    List<String> actualPrefixArray = new ArrayList<>();
    CACHE_KEY_PREFIX[] yourEnums = CACHE_KEY_PREFIX.values();

    Field[] cacheNames = 
      CACHE_KEY_PREFIX.KeyPrefix.class.getDeclaredFields();

    //list of expected prefixes
    for (Field field : cacheNames) {
        field.setAccessible(true);


       expectedPrefixArray.add(String.valueOf(
                   field.get(CACHE_KEY_PREFIX.KeyPrefix.class)));



    }

    //list of actual prefixes
    for (int i = 0; i < yourEnums.length; i++) {
        String[] prefix = CACHE_KEY_PREFIX.values()[i].prefixArray;
        for (int j = 0; j < CACHE_KEY_PREFIX.values()[i].prefixArray.length; 
  j++) {
            actualPrefixArray.add(prefix[j]);
        }
    }