清单 2-3. 使用反射检查数组类型和长度
public class ArrayReflection {
public static void main (String args[]) {
printType(args);
}
private static void printType (Object object) {
Class type = object.getClass();
if (type.isArray()) {
Class elementType = type.getComponentType();
System.out.println("Array of: " + elementType);
System.out.println(" Length: " + Array.getLength(object));
}
}
}
运行时创建数组：
int array[] = (int[])Array.newInstance(int.class, 5);
int dimensions[] = {5};
int array[] = (int[])Array.newInstance(int.class, dimensions);
int dimensions[] = {3, 4};
int array[][] = (int[][])Array.newInstance(int.class, dimensions);
int dimensions[] = {5,4,3,2,1};
int array[][][][][] = (int[][][][][])Array.newInstance(int.class, dimensions);
import java.lang.reflect.Array;
import java.util.Random;
public class ArrayCreate {
public static void main (String args[]) {
Object array = Array.newInstance(int.class, 3);
printType(array);
fillArray(array);
displayArray(array);
}
private static void printType (Object object) {
Class type = object.getClass();
if (type.isArray()) {
Class elementType = type.getComponentType();
System.out.println("Array of: " + elementType);
System.out.println("Array size: " + Array.getLength(object));
}
}
private static void fillArray(Object array) {
int length = Array.getLength(array);
Random generator = new Random(System.currentTimeMillis());
for (int i=0; i<length; i++) {
int random = generator.nextInt();
Array.setInt(array, i, random);
}
}
private static void displayArray(Object array) {
int length = Array.getLength(array);
for (int i=0; i<length; i++) {
int value = Array.getInt(array, i);
System.out.println("Position: " + i +", value: " + value);
}
}
}
运行时，输出将如下所示（尽管随机数会不同）：
Array of: int
Array size: 3
Position: 0, value: -54541791
Position: 1, value: -972349058
Position: 2, value: 1224789416
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