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在Java中,引用类型中有那么几个特殊的类,Object类是所有类的起源、Class类定义所有类的抽象与行为、ClassLoader类实现了类从.class文件中加载进jvm,而Array数组类,则实现了数组手动的创建。
Array数组类,是个不可被继承的类:
public final
class Array {
private Array() {}
}
而且构造方法是私有的,不能直接创建该类,其中有两种创造数组的方法,第一种格式如下:
public static Object newInstance(Class<?> componentType, int length)
throws NegativeArraySizeException {
return newArray(componentType, length);
}
private static native Object newArray(Class<?> componentType, int length)
throws NegativeArraySizeException;
它调用的newArray是native方法,它接受两个参数,一个Class类对象表明数组存贮的内容,另外一个表明数组的长度。如下面示例代码:
public class Test {
public static void main(String args[]) throws ClassNotFoundException, IllegalAccessException, InstantiationException, NoSuchMethodException, InvocationTargetException, NoSuchFieldException {
int []test= (int[]) Array.newInstance(int.class,10);
for (int i=0;i<test.length;i++){
test[i]=1;
}
for (int i=0;i<test.length;i++){
System.out.print(test[i]+" ");
}
}
//输出为:1 1 1 1 1 1 1 1 1 1
另外一种格式是用来创造多维数组的,其源码如下:
public static Object newInstance(Class<?> componentType, int... dimensions)
throws IllegalArgumentException, NegativeArraySizeException {
return multiNewArray(componentType, dimensions);
}
private static native Object multiNewArray(Class<?> componentType,
int[] dimensions)
throws IllegalArgumentException, NegativeArraySizeException;
它接受一个Class类对象,以及一个dimensions可变数组来输入的n维。比如创建一个二维数组,如下代码所示:
public class Test {
public static void main(String args[]) throws ClassNotFoundException, IllegalAccessException, InstantiationException, NoSuchMethodException, InvocationTargetException, NoSuchFieldException {
int [][]test= (int[][]) Array.newInstance(int.class,2,2);
for (int i=0;i<test.length;i++){
for (int j=0;j<test[i].length;j++){
test[i][j]=1;
}
}
for (int i=0;i<test.length;i++){
for (int j=0;j<test[i].length;j++){
System.out.print(test[i][j]+" ");
}
System.out.println();
}
}
}
剩余的几个重要的方法就不一一讲解了,在这里列出来:
//获取其数组长度
public static native int getLength(Object array)
throws IllegalArgumentException;
//获取指定索引的值
public static native Object get(Object array, int index)
throws IllegalArgumentException, ArrayIndexOutOfBoundsException;
//设置指定索引的值
public static native void set(Object array, int index, Object value)
throws IllegalArgumentException, ArrayIndexOutOfBoundsException;