In Java if else judgment under the condition of the else execution is not the problem-CodePudding

Package LeiHeDuiXiang;

import java.util.Scanner;

Public class CusttomeBiz {
String [] names=new String [30].

//add name
Public void addname (String name) {
for(int i=0; iIf (names [I]==null) {
Names [I]=name;
break;
}
}
}
//output name
Public void showname () {
System. The out. Println (" customer name list ");
for(int i=0; iIf (names [I]!=null) {
System. The out. Print (names [I] + "\ t");
}
}
}
//modify the customer name
//oldname old customer name
//newname new customer name
Public Boolean editname (String oldname, String newname) {
Boolean find=false;
for(int i=0; iIf (names [I] equals (oldname)) {
Names [I]=newname;
The find=true;
break;
}
}
Return the find;

}
Public static void main (String [] args) {
Scanner input=new Scanner(System.in);
CusttomeBiz ab=new CusttomeBiz ();
for(int i=0; i<5; I++) {
System. The out. Print (" please input the customer's name: ");
String newname=input. Next ();
Ab. Addname (newname);
}
Ab. Showname ();

System. The out. Println (" please input to modify the user name: ");
String oldname=input. Next ();
System. The out. Println (" please enter a new user name: ");
String newname=input. Next ();
System. The out. Println (" * * * * * * * * modify result * * * * * * * * ");
If (ab. Editname (oldname, newname)) {
System. The out. Println (" username change success ");
}
The else {
System. The out. Println (" the user was not found ");
}
Ab. Showname ();
}
}

When change the name of the existing can run
Modify the name does not exist when not

Welcome bosses give directions

CodePudding user response:

You this is an unusual, so will not enter the else, the exception is thrown directly,
Reason is mainly because your names [I] is null, because you only have 1, 2, 3, 4, 5, after (that is, names [5]) after the array element is null, and you input the oldname is 11, the for loop lookup, former names don't match [5] before, continue to find back again, just names [5] is null, namely becomes null. Equals (oldname), so a null pointer exception,

CodePudding user response:

Else covers too much, you don't have a name change, the pointer will find you to change the name, will be submitted to the null pointer exception, and not to say that you literally a wrong will return to you "do not check the user name"
If you enter modify user name is! # # $$... * & amp; The noise, he will still be submitted to the null pointer exception, but he should be quoted "illegal input name" error

Conclusion: you have too many else conditions include, should add more conditions

Suggestion: the else instead else if

CodePudding user response:

reference 1st floor qybao response:

you this is an unusual, so will not enter the else, the exception is thrown directly,
Reason is mainly because your names [I] is null, because you only have 1, 2, 3, 4, 5, after (that is, names [5]) after the array element is null, and you input the oldname is 11, the for loop lookup, former names don't match [5] before, continue to find back again, just names [5] is null, namely becomes null. Equals (oldname), so a null pointer exception,

Ok thank you understand

CodePudding user response:

refer to the second floor debugEDM response:

else covers too much, you don't have a name change, the pointer will find you to change the name, will be submitted to the null pointer exception, and not to say that you literally a wrong will return to you "do not check the user name"
If you enter modify user name is! # # $$... * & amp; The noise, he will still be submitted to the null pointer exception, but he should be quoted "illegal input name" error

Conclusion: you have too many else conditions include, should add more conditions

Suggestion: the else instead else if

Ok thank you for your understand

CodePudding user response:

reference 1st floor qybao response:

you this is an unusual, so will not enter the else, the exception is thrown directly,
Reason is mainly because your names [I] is null, because you only have 1, 2, 3, 4, 5, after (that is, names [5]) after the array element is null, and you input the oldname is 11, the for loop lookup, former names don't match [5] before, continue to find back again, just names [5] is null, namely becomes null. Equals (oldname), so a null pointer exception,

Can use the try catch final processing? Specific what

CodePudding user response:

To keep logic, can now add try in editname catch
For example,
Try {
for (int i=0; iIf (names [I] equals (oldname)) {
Names [I]=newname;
The find=true;
break;
}
}
} the catch (Exception e) {
//donothing
}
Normally, however, the known names have null element in array, you should avoid null comparison, so would be better to change the following
Try {
for (int i=0; iIf (names [I]==null) continue;//if null will not compare, continue to look for the next
If (names [I] equals (oldname)) {
Names [I]=newname;
The find=true;
break;
}
}
} the catch (Exception e) {
//donothing
}

CodePudding user response:

refer to 6th floor qybao response:

to keep current logic, can add the try in editname catch
For example,
Try {
for (int i=0; iIf (names [I] equals (oldname)) {
Names [I]=newname;
The find=true;
break;
}
}
} the catch (Exception e) {
//donothing
}
Normally, however, the known names have null element in array, you should avoid null comparison, so would be better to change the following
Try {
for (int i=0; iIf (names [I]==null) continue;//if null will not compare, continue to look for the next
If (names [I] equals (oldname)) {
Names [I]=newname;
The find=true;
break;
}
}
} the catch (Exception e) {
//donothing
}

Ok thank you understand