Java Object-Array copy with 1 less

Question

public void arrayUpdate(int counter,int counter2){
    int counterShipMemory=0;
    this.playerMemory2= new Player[this.playerMemory.length];
    for(int i = 0; i< this.playerMemory.length;i++){
    this.playerMemory2[i] = this.playerMemory[i];
    }
    this.playerMemory2[counter].shipMemory= new Ship[this.playerMemory2[counter].shipMemory.length-1];
    for(int counter3=0;counter3 <this.playerMemory[counter].shipMemory.length;counter3++){
        if(counter3!=counter2){
            this.playerMemory2[counter].shipMemory[counterShipMemory]=this.playerMemory[counter].shipMemory[counter3];
            counterShipMemory++;
        }
    }
    this.playerMemory[counter].shipMemory = new Ship[playerMemory2[counter].shipMemory.length];
    for(int counter3=0;counter3 <playerMemory2[counter].shipMemory.length;counter3++){
        this.playerMemory[counter].shipMemory[counter3]=playerMemory2[counter].shipMemory[counter3];
    }

说明： counter 是一个玩家的数组 ID。

counter2 是应该移除的飞船的数组 ID。

问题在第 7 行 (this.playerMemory2[counter].shipMemory= new Ship)。

如果我开始这一行，playerMemory2 处的 shipMemory 和 playerMemory 会发生变化。但为什么？我该如何解决这个问题？

Answer 1

它们都改变了，因为它们是同一个对象：

for(int i = 0; i < this.playerMemory.length; i++){
    this.playerMemory2[i] = this.playerMemory[i];
}

在这个循环中，两个数组引用相同的对象（playerMemory[i] == playerMemory2[i]，相同内存地址的对象）。因此，如果你改变了playerMemory2[i]的shipMemory，你也改变了playerMemory[i]的shipMemory。

为防止这种情况，您可以克隆每个对象。如果您实现了 clone() 方法，这将是一个简单的修复方法：

for(int i = 0; i < this.playerMemory.length; i++){
    this.playerMemory2[i] = this.playerMemory[i].clone();
}

现在，只有 playerMemory2[i] 的 shipMemory 会改变。

Java Object-Array copy with 1 less

Java Object-Array copy with 1 less

java

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