6.13. Chapter Summary

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Chapter Summary

• A variable is declared as an array type using the syntax dataType[] arrayRefVar or dataType arrayRefVar[] . The style dataType[] arrayRefVar is preferred, although dataType arrayRefVar[] is legal.

• Unlike declarations for primitive data type variables , the declaration of an array variable does not allocate any space in memory for the array. An array variable is not a primitive data type variable. An array variable contains a reference to an array.

• You cannot assign elements to an array unless it has already been created. You can create an array by using the new operator with the following syntax: new dataType[arraySize] .

• Each element in the array is represented using the syntax arrayRefVar[index] . An index must be an integer or an integer expression.

• After an array is created, its size becomes permanent and can be obtained using arrayRefVar.length . Since the index of an array always begins with , the last index is always arrayRefVar.length - 1 . An out-of-bounds error will occur if you attempt to reference elements beyond the bounds of an array.

• Programmers often mistakenly reference the first element in an array with index 1 , so that the index of the tenth element becomes 10 . This is called the index off-by-one error .

• Java has a shorthand notation, known as the array initializer , which combines declaring an array, creating an array, and initializing in one statement using the syntax:

     dataType[] arrayRefVar = {value0, value1, ..., value  k  }   . 

  
  

• When you pass an array argument to a method, you are actually passing the reference of the array; that is, the called method can modify the elements in the caller's original array.

• You can use arrays of arrays to form multidimensional arrays. For example, a two-dimensional array is declared as an array of arrays using the syntax dataType[][] arrayRefVar or dataType arrayRefVar[][] .