java 表达式的类型必须是数组类型，但解析为Object
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The type of an expression must be an array type, but it is resolved to Object
提问by Anderson Green
I expected this to compile, but I kept getting the error "The type of an expression must be an array type, but it is resolved to Object". Is there a simple workaround for this?
我希望它能够编译，但我一直收到错误“表达式的类型必须是数组类型，但它已解析为对象”。有一个简单的解决方法吗？
public class NodeTest {
public static void main(String[] args) {
Object[] arr = new Object[5]; // each element of object will be an array of integers.
for(int i = 0; i < 5; i++){
int[][] a = new int[2*(i+1)][2*(i+1)];
arr[i] = a;
}
arr[0][0][0] = 0; //error here
}
}
}
回答by Brett Walker
arris Object[]so arr[0]will return an Object
arr是Object[]这样arr[0]会返回一个Object
But since you know that arrcontains int[][]as instance of Objectyou will have to cast them to be so.
但是既然你知道arr包含int[][]作为实例，Object你就必须将它们转换成这样。
( ( int[][] ) arr[0] )[0][0] = 0;
回答by Paul Bellora
You want to declare arras int[][][]rather than Object[]. While arrays are of type Objectso the assignment in the loop is legal, you're then losing that type information so the compiler doesn't know the elements of arrare int[][]in the bottom line.
您想声明arr为 asint[][][]而不是Object[]。虽然阵列式Object所以在循环分配是合法的，你再失去该类型的信息，以便编译器不知道的元素arr都int[][]在底线。
int[][][] arr = new int[5][][];
for(int i = 0; i < arr.length; i++) { //good practice not to hardcode 5
arr[i] = new int[2*(i+1)][2*(i+1)];
}
arr[0][0][0] = 0; //compiles
回答by Manish Singh
I would suggest think from the logic perspective rather than work around.
我建议从逻辑的角度思考而不是解决问题。
You are trying to use multidimensional arrays , your looping is in a single dimension{which might be right as per your requirements}. Can you post the pseudo code, this might help
您正在尝试使用多维数组，您的循环是单维的{这可能符合您的要求}。你可以发布伪代码，这可能会有所帮助
This also works
这也有效
public class NodeTest {
public static void main(String[] args) {
Object[] arr = new Object[5]; // each element of object will be an array
// of integers.
for (int i = 0; i < 5; i++) {
int[][] a = new int[2 * (i + 1)][2 * (i + 1)];
arr[i] = a;
}
arr[0] = 0; // Make it one dimensional
}
}
