?? ex1(2).java
字號:
// arrays/Ex1.java
// TIJ4 Chapter Arrays, Exercise 1, page 752
/* Create a method that takes an array of BerylliumSphere as an argument.
* Call the method, creating the argument dynamically. Demonstrate that
* ordinary aggregate array intitialization doesn't work in this case.
* Discover the only situations where ordinary aggregate array initialization
* works, and where dynamic aggregate array initialization is redundant.
*/
import java.util.*;
import static net.mindview.util.Print.*;
class A { public String toString() { return "A Object"; } }
public class Ex1 {
// Method that takes BerylliumSphere[] as argument
// and prints the argument as array elements and as List or String:
public static void test(BerylliumSphere[] a) {
print(Arrays.asList(a));
}
// Generic version:
public static <T> void test(T[] t) {
print(Arrays.asList(t));
}
// int version:
public static void test(int[] ia) {
print(Arrays.toString(ia));
}
public static void main(String[] args) {
print("For objects, e.g., BerylliumSpheres:");
// Array is created and initialized (aggregate initialization)
// but all elements are null, not BerylliumSpheres:
test(new BerylliumSphere[3]);
// Dynamic aggregate initialization works;
// elements are now BerylliumSpheres:
test(new BerylliumSphere[]{
new BerylliumSphere(), new BerylliumSphere() });
// Aggregate initialization this way works:
BerylliumSphere[] a = { new BerylliumSphere(),
new BerylliumSphere(), new BerylliumSphere() };
test(a);
// Elements initialized to null:
BerylliumSphere[] bsa = new BerylliumSphere[2];
test(bsa);
bsa = a;
test(bsa);
print("-------------");
print("For primitives, e.g., int:");
// Dynamic aggregate initialization works:
test(new int[]{ new Integer(0), new Integer(0) });
// But may be considered redundant, since
// aggregate initialization works:
// elements initialized to zero (not null):
test(new int[2]);
// Ordinary aggregate initialization this way also works:
int[] ia = { 1, 2, 3, };
test(ia);
}
}
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