java - 方法更改参数的值

Question

方法(Mover)属于 Estado 类，它描述了带有矩阵 tablero(board)和跟踪空位置的变量 Hueco(hole)的滑动拼图的状态。问题是该函数改变了原始 Estado 的值，这是不应该的。有人可以告诉我我做错了什么吗？

public class Estado {
public int dim;
public int tablero[][];
public int hueco[]= new int[2];
public Estado(int dim,int tablero[][],hueco){
    this.dim=dim;
    this.tablero=tablero;
    this.hueco=hueco;

}
public Estado(){}

//moves empty tile to one of 4 option(up,down,right,left)
(up,down,right,left)
//
public Estado mover(String direccion,Estado estado){
    Estado sig= new Estado();        
    sig.tablero=estado.tablero;
    sig.dim=estado.dim;
    sig.hueco=estado.hueco;
    estado.mostrarTablero();
    switch (direccion){
        case "up":                
            sig.tablero[estado.hueco[0]][estado.hueco[1]]=sig.tablero[estado.hueco[0]+1][estado.hueco[1]];
            sig.tablero[estado.hueco[0]+1][estado.hueco[1]]=0;
            sig.hueco[0]=estado.hueco[0]+1;
            break;               
        default:
//cases "down,right and left" omitted, very similar to "up"
            break;
    }               
    return sig;

}                                        
}

Answer 1

问题是变量sig指向参数estado的相同数组tablero和hueco，因为本声明的内容:

sig.tablero=estado.tablero;
sig.hueco=estado.hueco;

当您调用 mover 方法时，Java 会传递“指针”的副本，但不会传递数组结构的平面副本 (copia plana)。

也许您更喜欢了解按值传递、按引用传递主题以及制作平面副本的含义。

编辑:我取自 Programmers StackExchange这应该可以帮助您理解:

Java is pass by value. Think of it like a pointer language like C, the value of the pointer (memory address) is being passed, so you have a reference to the same object. Primitives aren't stored internally the same way as Objects, so when you pass a primitive's value, it's the content, not a pointer.