Throws Nullpointer exception when calls parent class method from child class In JAVA

This is Parent class

public class RequestDTO implements Serializable {
private static final long serialVersionUID = 1L;
private String paymentProvider;
private Boolean isEncrypt;
public RequestDTO() {
}
public RequestDTO(String paymentProvider,
Boolean isEncrypt) {
super();
this.paymentProvider = paymentProvider;
this.isEncrypt = isEncrypt;
}
public void setPaymentProvider(String paymentProvider) {
this.paymentProvider = paymentProvider;
}
public Boolean getIsEncrypt() {
return isEncrypt;
}
public void setIsEncrypt(Boolean isEncrypt) {
if (isEncrypt == null) {
this.isEncrypt = false;
} else {
this.isEncrypt = isEncrypt;
}
}
}

Below is child class

   public class CardDetailsDTO extends RequestDTO {
private static final long serialVersionUID = 1L;
private String cardNumber;
private String expiryDate;
private String cardHolderName;
private String cardType;
private String cardIssueDate;
private String cardIssueNo;
private String modifyDummyCardNumber(String cardNum) {
String dummyCardNumber ;
if (cardNum != null && !cardNum.isEmpty() && this.getIsEncrypt() != true) {
dummyCardNumber = "************" + cardNum.substring(12);
return dummyCardNumber;
} else {
return "********";
}
}
public String getCardNumber() {
return cardNumber;
}
public void setCardNumber(String cardNumber) {
this.cardNumber = cardNumber;
}
public String getExpiryDate() {
return expiryDate;
}
public void setExpiryDate(String expiryDate) {
this.expiryDate = expiryDate;
}
public String getCardHolderName() {
return cardHolderName;
}
public void setCardHolderName(String cardHolderName) {
this.cardHolderName = cardHolderName;
}
public String getCardType() {
return cardType;
}
public void setCardType(String cardType) {
this.cardType = cardType;
}
public String getCardIssueDate() {
return cardIssueDate;
}
public void setCardIssueDate(String cardIssueDate) {
this.cardIssueDate = cardIssueDate;
}
public String getCardIssueNo() {
return cardIssueNo;
}
public void setCardIssueNo(String cardIssueNo) {
this.cardIssueNo = cardIssueNo;
}
@Override
public String toString() {
StringBuilder builder = new StringBuilder();
builder.append("CardDetailsDTO [expiryDate=");
builder.append(expiryDate);
builder.append(", cardHolderName=");
builder.append(cardHolderName);
builder.append(", cardType=");
builder.append(cardType);
builder.append(", cardIssueDate=");
builder.append(cardIssueDate);
builder.append(", cardIssueNo=");
builder.append(cardIssueNo);
builder.append(", dummyCardNumber=");
builder.append(modifyDummyCardNumber(getCardNumber()));
builder.append("]");
return builder.toString();
}
}

when I called

> modifyDummyCardNumber

method inside child class toString method it throws null pointer exception because I called this.getIsEncrypt() inside modifyDummyCardNumber method if statement as showing above ,but when I sout the isEncrypt value from the parent class it shows as "true",
How to use the parent class variable value in child class?

There is one problem in this code: the class RequestDTO has a constructor without arguments, which means that it can throw NullPointerException if the variables of this class are not defined before using this constructor (this might be why it throws you NullPointerException).

You can also assign default values on the declaration of each variable of the class.

Anyway this code shouldn't throw any NullPointerException if the variable isEncrypt is assigned to any value.

Since isEncrypt is never set, it is null by default.

The term getIsEncrypt()! = false tries to unbox the null as bool, which fails.

Do

public class RequestDTO implements Serializable {
// ...
private boolean isEncrypt;
// ...
}

and, while you're at it

if (cardNum != null && !cardNum.isEmpty() && !this.getIsEncrypt()) {

To avoid this kind of errors change the type of isEncrypted field to boolean(primitive type).