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| No. | Answer | Remark | |
|---|---|---|---|
| 1 | a e | 1 5 | An array creation expression must have either a dimension expression or an initializer. If both are present, then a compile-time error is generated. Similarly, if neither is present, then a compile-time error is generated. If only the dimension expression is present, then an array with the specified dimension is created with all elements set to the default values. If only the initializer is present, then an array will be created that has the required dimensions to accommodate the values specified in the initializer. Java avoids the possibility of an incompatible dimension expression and initializer by not allowing both to appear in the same array creation expression. A compile-time error is generated by the array creation expression for a1, because it needs either a dimension expression or an initializer. A compile-time error is generated at 5, because either the dimension expression or the initializer must be removed. |
| 2 | b | Prints: 0,0,0.0,null | Each array contains the default value for its type. The default value of a primitive byte or a primitive long is printed as 0. The default value of a float primitive is printed as 0.0. The default value of an Object is null and is printed as null. |
| 3 | e | Prints: 2,5,8 | Arrays a1, a2 and a3 all contain 3 integers. The first element of the array has an index of 0 so an index of one refers to the second element of each array. |
| 4 | a | 1 | A compile-time error occurs at the line marked 1, because the array reference declaration can not be used to declare the number of components contained in the array. Instead, the dimension expression should be contained in an array creation expression such as new int[5]. |
| 5 | e | Compile-time error | Variable b1 is initialized to false, because it is a class member. The array component array[0] is initialized to the default value, false, of the array type, boolean[], even though the array is declared locally. Local variable b2 is not initialized, because it is local. A compile-time error is generated by the statement that attempts to print the value of b2. |