Arrays.copyOf()方法说明

调用Arrays.copyOf()方法会在堆中重新分配内存创建数组

 

代码翻译：

/传入原有数组对象，传入要截取的长度
    public static <T> T[] copyOf(T[] original, int newLength) {
        return (T[]) copyOf(original, newLength, original.getClass());
    }
    
    //传入原有数组对象，传入要截取的长度、数组中的类newType
    public static <T,U> T[] copyOf(U[] original, int newLength, Class<? extends T[]> newType) {
        @SuppressWarnings("unchecked")
        //新建一个长度为newLenth的数组
        T[] copy = ((Object)newType == (Object)Object[].class)
            ? (T[]) new Object[newLength]
            : (T[]) Array.newInstance(newType.getComponentType(), newLength);
        //通过System.arraycopy方法将原有数组拷贝到新的数组中，最后返回新数组
        System.arraycopy(original, 0, copy, 0,
                         Math.min(original.length, newLength));
        return copy;
    }

测试：

    public static void main(String[] args) {
        String[] arrayOld = {"1","2"};
        System.out.println(JSONObject.toJSONString(arrayOld));
        System.out.println("arrayOld="+arrayOld);
        String[] araryNew = arrayOld;
        System.out.println(JSONObject.toJSONString(araryNew));
        System.out.println("araryNew="+araryNew);
        String[] araryCopy = Arrays.copyOf(araryNew, araryNew.length);
        System.out.println(JSONObject.toJSONString(araryCopy));
        System.out.println("araryCopy="+araryCopy);
    }

执行结果：

["1","2"]

arrayOld=[Ljava.lang.String;@60f82f98

["1","2"]

araryNew=[Ljava.lang.String;@60f82f98

["1","2"]

araryCopy=[Ljava.lang.String;@35f983a6

 

arrayOld与araryCopy对象不同，说明 Arrays.copyOf()会在堆中重新分配内存创建数组