Java内存空间重叠？

Question

我在将元素添加到 ArrayList 时遇到了问题。每次我执行“添加”时，整个数组内容都会替换为当前元素值。我最终得到了例如。 10 个重复的元素副本。

类(class)设置如下:

public class BradfordReport {
    EmployeeRow _empRow = new EmployeeRow();
    ArrayList<EmployeeRow> _bradfordData = new ArrayList<EmployeeRow>();

    public void Run() {
       // processing to setup Employee row variables
       for (int x=0; x<10; x++) {
           // This next line in debug IS ADJUSTING THE ARRAYLIST DATA!!
           _empRow.EmpNum = x; // etc for other variable in EmployeeRow
           _bradfordData.add(er);
       }
    }
    // THE RESULT IN _bradfordData is 10 elements, all with EmpNum = 10!
 }

public class EmployeeRow {
    int EmpNum;
    string EmpNm; // etc.
 }

我在这里混淆了 Java 内存分配吗？ EmployeeRow 变量和 ArrayList 似乎共享相同的内存空间 - 非常奇特。谢谢大家

Answer 1

您正在将 EmployeeRow 类的相同实例添加到数组列表中。尝试类似的东西:

public class BradfordReport {
    EmployeeRow _empRow = new EmployeeRow();
    ArrayList<EmployeeRow> _bradfordData = new ArrayList<EmployeeRow>();

    public void Run() {
       // processing to setup Employee row variables
       for (int x=0; x<10; x++) {
           // create a NEW INSTANCE of an EmployeeRow
           _empRow = new EmployeeRow();
           _empRow.EmpNum = x; // etc for other variable in EmployeeRow
           _bradfordData.add(_empRow);
       }
    }
    // THE RESULT IN _bradfordData is 10 elements, all with EmpNum = 10!
}

public class EmployeeRow {
    int EmpNum;
    string EmpNm; // etc.
 }