How to check if array element is null to avoid NullPointerException in Java

Question

I have a partially nfilled array of objects  and when I iterate through them I tried to check to see whether the selected object is null before I do other stuff with it  However  even the act of checking if it is null seem to through a NullPointerException  array length will include all null elements as well  How do you go about checking for null elements in an array  For example in the following code will throw an NPE for me   Object     someArray   new Object 5     for  int i 0  i lt  someArray length-1  i          if  someArray i   null      do something

User · Answer

Fighting whether the code is compiling or not I would say create a array of sixe 5 add 2 values and print them   you will get the two values and others are null  The question is although the size is 5 but there are 2 objects in the array   How to find how many objects are present in the array

User · Answer

The given code works for me   Notice that someArray i  is always null since you have not initialized the second dimension of the array

User · Answer

You have more going on than you said   I ran the following expanded test from your example   public class test        public static void main String   args            Object     someArray   new Object 5             someArray 0    new Object 10           someArray 1    null          someArray 2    new Object 1           someArray 3    null          someArray 4    new Object 5            for  int i 0  i lt  someArray length-1  i                  if  someArray i     null                    System out println  not null                  else                   System out println  null                                      and got the expected output      cygdrive c Program  Files Java jdk1 6 0 03 bin java -cp   test not null null not null null not null   Are you possibly trying to check the lengths of someArray index

User · Answer

The given code works for me   Notice that someArray i  is always null since you have not initialized the second dimension of the array

User · Answer

You have more going on than you said   I ran the following expanded test from your example   public class test        public static void main String   args            Object     someArray   new Object 5             someArray 0    new Object 10           someArray 1    null          someArray 2    new Object 1           someArray 3    null          someArray 4    new Object 5            for  int i 0  i lt  someArray length-1  i                  if  someArray i     null                    System out println  not null                  else                   System out println  null                                      and got the expected output      cygdrive c Program  Files Java jdk1 6 0 03 bin java -cp   test not null null not null null not null   Are you possibly trying to check the lengths of someArray index

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public static void main String s          int firstArray      2  14  6  82  22       int secondArray      3  16  12  14  48  96       int number   getCommonMinimumNumber firstArray  secondArray       System out println  The number is     number      public static int getCommonMinimumNumber int firstSeries    int secondSeries          Integer result  0      if   firstSeries length   0  amp  amp  secondSeries length   0                 series firstSeries           series secondSeries           one   for  int i   0   i  lt  firstSeries length  i                          for  int j   0  j  lt  secondSeries length  j                    if   firstSeries i    secondSeries j                                         result  firstSeries i                       break one                                    else                     result   -999                      else if   firstSeries    Null    secondSeries    null          result  -999       else         result   -999       return result     public static int   series int number           int temp      boolean fixed   false      while fixed    false                fixed   true          for   int i  0   i  lt  number length-1  i                          if   number i   gt  number i 1                                 temp   number i 1                   number i 1    number i                   number i    temp                  fixed   false                                      for   int i  0  i lt  number length i        System out print number i              return number

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String labels        MH   null   AP    KL    CH    MP    GJ    OR       if Arrays toString labels  indexOf  null    gt  -1         System out println  Array Element Must not be null                          or      throw new Exception  Array Element Must not be null              ------------------------------------------------------------------------------------------           For two Dimensional array  String labels2           MH   null   AP    KL    CH    MP    GJ    OR       MH    FG    AP    KL    CH    MP    GJ    OR          if Arrays deepToString labels2  indexOf  null    gt  -1         System out println  Array Element Must not be null                      or      throw new Exception  Array Element Must not be null          ------------------------------------------------------------------------------------------  same for Object Array      String ObjectArray           MH   null   AP    KL    CH    MP    GJ    OR       MH    FG    AP    KL    CH    MP    GJ    OR          if Arrays deepToString ObjectArray  indexOf  null    gt  -1         System out println  Array Element Must not be null                   or      throw new Exception  Array Element Must not be null          If you want to find a particular null element  you should use for loop as above said

User · Answer

Well  first of all that code doesn t compile   After removing the extra semicolon after i    it compiles and runs fine for me

User · Answer

Fighting whether the code is compiling or not I would say create a array of sixe 5 add 2 values and print them   you will get the two values and others are null  The question is although the size is 5 but there are 2 objects in the array   How to find how many objects are present in the array

User · Answer

The given code works for me   Notice that someArray i  is always null since you have not initialized the second dimension of the array

User · Answer

It does not   See below  The program you posted runs as supposed   C  oreyes samples java arrays gt type ArrayNullTest java public class ArrayNullTest       public static void main  String    args             Object     someArray   new Object 5                 for  int i 0  i lt  someArray length-1  i                       if  someArray i   null                          System out println  It wasn t null                       else                        System out printf  Element at  d was null  n   i                                                 C  oreyes samples java arrays gt javac ArrayNullTest java  C  oreyes samples java arrays gt java ArrayNullTest Element at 0 was null Element at 1 was null Element at 2 was null Element at 3 was null Element at 4 was null  C  oreyes samples java arrays gt

User · Answer

You have more going on than you said   I ran the following expanded test from your example   public class test        public static void main String   args            Object     someArray   new Object 5             someArray 0    new Object 10           someArray 1    null          someArray 2    new Object 1           someArray 3    null          someArray 4    new Object 5            for  int i 0  i lt  someArray length-1  i                  if  someArray i     null                    System out println  not null                  else                   System out println  null                                      and got the expected output      cygdrive c Program  Files Java jdk1 6 0 03 bin java -cp   test not null null not null null not null   Are you possibly trying to check the lengths of someArray index

User · Answer

It does not   See below  The program you posted runs as supposed   C  oreyes samples java arrays gt type ArrayNullTest java public class ArrayNullTest       public static void main  String    args             Object     someArray   new Object 5                 for  int i 0  i lt  someArray length-1  i                       if  someArray i   null                          System out println  It wasn t null                       else                        System out printf  Element at  d was null  n   i                                                 C  oreyes samples java arrays gt javac ArrayNullTest java  C  oreyes samples java arrays gt java ArrayNullTest Element at 0 was null Element at 1 was null Element at 2 was null Element at 3 was null Element at 4 was null  C  oreyes samples java arrays gt

User · Answer

The example code does not throw an NPE   there also should not be a     behind the i

User · Answer

The given code works for me   Notice that someArray i  is always null since you have not initialized the second dimension of the array

User · Answer

Well  first of all that code doesn t compile   After removing the extra semicolon after i    it compiles and runs fine for me

User · Answer

The example code does not throw an NPE   there also should not be a     behind the i

User · Answer

String labels        MH   null   AP    KL    CH    MP    GJ    OR       if Arrays toString labels  indexOf  null    gt  -1         System out println  Array Element Must not be null                          or      throw new Exception  Array Element Must not be null              ------------------------------------------------------------------------------------------           For two Dimensional array  String labels2           MH   null   AP    KL    CH    MP    GJ    OR       MH    FG    AP    KL    CH    MP    GJ    OR          if Arrays deepToString labels2  indexOf  null    gt  -1         System out println  Array Element Must not be null                      or      throw new Exception  Array Element Must not be null          ------------------------------------------------------------------------------------------  same for Object Array      String ObjectArray           MH   null   AP    KL    CH    MP    GJ    OR       MH    FG    AP    KL    CH    MP    GJ    OR          if Arrays deepToString ObjectArray  indexOf  null    gt  -1         System out println  Array Element Must not be null                   or      throw new Exception  Array Element Must not be null          If you want to find a particular null element  you should use for loop as above said

User · Answer

The example code does not throw an NPE   there also should not be a     behind the i

User · Answer

You have more going on than you said   I ran the following expanded test from your example   public class test        public static void main String   args            Object     someArray   new Object 5             someArray 0    new Object 10           someArray 1    null          someArray 2    new Object 1           someArray 3    null          someArray 4    new Object 5            for  int i 0  i lt  someArray length-1  i                  if  someArray i     null                    System out println  not null                  else                   System out println  null                                      and got the expected output      cygdrive c Program  Files Java jdk1 6 0 03 bin java -cp   test not null null not null null not null   Are you possibly trying to check the lengths of someArray index

User · Answer

You can do it on one line of code  without array declaration    object   someArray   new object           aaaa       3      null    bool containsSomeNull   someArray Any x   gt  x    null

User · Answer

The example code does not throw an NPE   there also should not be a     behind the i

User · Answer

It does not   See below  The program you posted runs as supposed   C  oreyes samples java arrays gt type ArrayNullTest java public class ArrayNullTest       public static void main  String    args             Object     someArray   new Object 5                 for  int i 0  i lt  someArray length-1  i                       if  someArray i   null                          System out println  It wasn t null                       else                        System out printf  Element at  d was null  n   i                                                 C  oreyes samples java arrays gt javac ArrayNullTest java  C  oreyes samples java arrays gt java ArrayNullTest Element at 0 was null Element at 1 was null Element at 2 was null Element at 3 was null Element at 4 was null  C  oreyes samples java arrays gt

User · Answer

You can do it on one line of code  without array declaration    object   someArray   new object           aaaa       3      null    bool containsSomeNull   someArray Any x   gt  x    null

User · Answer

Well  first of all that code doesn t compile   After removing the extra semicolon after i    it compiles and runs fine for me

User · Answer

public static void main String s          int firstArray      2  14  6  82  22       int secondArray      3  16  12  14  48  96       int number   getCommonMinimumNumber firstArray  secondArray       System out println  The number is     number      public static int getCommonMinimumNumber int firstSeries    int secondSeries          Integer result  0      if   firstSeries length   0  amp  amp  secondSeries length   0                 series firstSeries           series secondSeries           one   for  int i   0   i  lt  firstSeries length  i                          for  int j   0  j  lt  secondSeries length  j                    if   firstSeries i    secondSeries j                                         result  firstSeries i                       break one                                    else                     result   -999                      else if   firstSeries    Null    secondSeries    null          result  -999       else         result   -999       return result     public static int   series int number           int temp      boolean fixed   false      while fixed    false                fixed   true          for   int i  0   i  lt  number length-1  i                          if   number i   gt  number i 1                                 temp   number i 1                   number i 1    number i                   number i    temp                  fixed   false                                      for   int i  0  i lt  number length i        System out print number i              return number

User · Answer

Well  first of all that code doesn t compile   After removing the extra semicolon after i    it compiles and runs fine for me

User · Answer

It does not   See below  The program you posted runs as supposed   C  oreyes samples java arrays gt type ArrayNullTest java public class ArrayNullTest       public static void main  String    args             Object     someArray   new Object 5                 for  int i 0  i lt  someArray length-1  i                       if  someArray i   null                          System out println  It wasn t null                       else                        System out printf  Element at  d was null  n   i                                                 C  oreyes samples java arrays gt javac ArrayNullTest java  C  oreyes samples java arrays gt java ArrayNullTest Element at 0 was null Element at 1 was null Element at 2 was null Element at 3 was null Element at 4 was null  C  oreyes samples java arrays gt

[java] How to check if array element is null to avoid NullPointerException in Java

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