Question

I’ve a Java Stack created and some custom objects added to it. These objects contains unique id as one of their field. I need to get the index of that object in stack based on the unique name. Please find the example.

class TestVO{

 private String name;
 private String uniqueId;
//getters and setters
}
public class TestStack{
 public static void main(String args[]){
  TestVO vo1=new TestVO();
TestVO vo2=new TestVO();
TestVO vo3=new TestVO();

vo1.setName("Test Name 1")
vo1.setId("123")

vo2.setName("Test name 2");
vo2.setId("234");

Stack<TestVO> stack=new Stack<TestVO>();
stack.add(vo1);
stack.add(vo2);

//I need to get the index of a VO from stack using it's unique ID
}

}

Can someone please help me to implement this?

Answer 1

First, implement the hashCode and equals methods for the TestVO class:

class TestVO{

 private String name;
 private String uniqueId;

 public boolean hashCode() {
  if (uniqueId == null) return 0;
  return uniqueId.hashCode();
 }

 public boolean equals(Object o) {
  if (o instanceof TestVO) {
   TestVO other = (TestVO) o;
   return o.uniqueId.equals(uniqueId);
  }
  return false;
 }
//getters and setters
}

Please note that in the equals method you should add extra code to check that o.uniqueId is not null.

Now you can find the index of a TestVO object using its uniqueId using this code:

int index = stack.indexOf(vo1);