Array Length in Java

Question

I declared an array as shown below   int   arr   new int 10     Then I assigned following values to the array   arr 0    1  arr 1    2  arr 2    3  arr 3    4    Then I declared and initialized an integer variable   int arrayLength   arr length    This will be useful to find actual size but is there any method to find logical size of the array

User · Answer

It contains the allocated size  10  The remaining indexes will contain the default value which is 0

User · Answer

It will contain the actual size of the array as that is what you initialized the array to be when you declared it  Java has no concept of the  logical  size of an array  as far as it is concerned the default value of 0 is just as logical as the values you have manually set

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Java arrays are actually fixed in size  and the other answers explain how  length isn t really doing what you d expect  I d just like to add that given your question what you might want to be using is an ArrayList  that is an array that can grow and shrink   https   docs oracle com javase 8 docs api java util ArrayList html  Here the  size   method will show you the number of elements in your list  and you can grow this as you add things

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Arrays are static memory allocation  so if you initialize an array of integers   int   intArray   new int 15     The length will be always 15  no matter how many indexes are filled   And another thing  when you intialize an array of integers  all the indexes will be filled with  0

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int array   new int 3     array length    so here we have created an array with a memory space of 3    this is how it looks actually   0th  1st 2nd               Index 2     4   5               Number  So as u see the size of this array is 3 but the index of array is only up to 2 since any array starts with 0th index   second statement  output shall be 3 since the length of the array is 3    Please don t get confused between the index value and the length of the array      cheers

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In this case  arr length will return 10  the size of array you allocated  Logical size doesn t really apply here  as this is a fixed length array   When you initialize the array   int   arr   new int 10     Java will create an array with 10 elements and initialize all of these to 0  See the Java language spec for details of initial values for this and other primitive types

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Arrays are allocated memory at compile time in java  so they are static  the elements not explicitly set or modified are set with the default values  You could use some code like this  though it is not recommended as it does not count default values  even if you explicitly initialize them that way  it is also likely to cause bugs down the line  As others said  when looking for the actual size   quot  length quot  must be used instead of  quot  length   quot   public int logicalArrayLength type   passedArray        int count   0      for  int i   0  i  lt  passedArray length  i              if  passedArray i     defaultValue                count                        return count

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In Java  your  actual  and  logical  size are the same  The run-time fills all array slots with default values upon allocation  So  your a contains 10

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First of all  length is a property  so it would be arr length instead of arr length     And it will return 10  the declared size  The elements that you do not declare explicitely are initialized with 0

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It should be   int a   arr length    Parenthesis should be avoided

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int   arr   new int 10     arr is an int type array which has size 10  It is an array of 10 elements  If we don t initialize an array by default array elements contains default value  In case of int array default value is 0   length is a property which is applicable for an array  here arr length will give 10

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int arr    4 7 2 21321 657 12321     int length  arr length    System out println length      will return 6    int arr2     new int 10      arr2 3    4    int length2  arr2 length    System out println length2         will return 10  all other digits will be 0 initialize because staic memory initialization

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if you mean by  logical size   the index of array  then simply     int arrayLength   arr length-1  since the the array index starts with  0   so the logical or  array index  will always be less than the actual size by  one

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It contains the allocated size  10  The unassigned indexes will contain the default value which is 0 for int

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If you want the logical size of the array  you can traverse all the values in the array and check them against zero  Increment the value if it is not zero and that would be the logical size  Because array size is fixed  you do not have any inbuilt method  may be you should have a look at collections

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To find length of an array A you should use the length property  It is as A length  do not use A length   its mainly used for size of string related objects     The length property will always show the total allocated space to the array during initialization    If you ever have any of these kind of problems the simple way is to run it  Happy Programming

[java] Array Length in Java

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