indexOf

[cerbain1]

Hi all
i have an arrayList of elements (string), i want to be ablew to retrieve the indexOf any element.
I have tried this but errors

public E indexOf (int index){
if (index<0 || index>=size)
throw new IndexOutOfBoundsException(""+index);

for(int i=0; i<size;i++ )
if (E[]theArray[i] = theArray[index])
r = theArray[index];
return r;
}

[sjalle]

You say arraylist, but you show ordinary arrays here ?

Anyway, the elements int the arraylist must either be
String, Boolean, Character or numeric (Integer, Float...) for the indexOf to
work, or the you have to have the

public boolean equals (Object ob)

method implemented in the class that you store in the list

Check this out

import java.util.*;
/**
 * Find index of an object in an arraylist
 */
class SomeClass {
  public String name=null;
  public int iD=-1;
  public SomeClass(String name, int iD) {
    this.name=name;
    this.iD=iD;
  }

  public boolean equals(Object ob) {
    if (!(ob instanceof SomeClass)) {
        return false;
    }
    SomeClass sC=(SomeClass)ob;
    return name.equals(sC.name) && iD == sC.iD;
  }

}

public class AList {
  ArrayList list=new ArrayList();
  public AList() {
    SomeClass sC1=new SomeClass("ABC",123);
    SomeClass sC2=new SomeClass("DEF",223);
    SomeClass sC3=new SomeClass("GHI",323);
    SomeClass sC4=new SomeClass("JKL",423);

    list.add(sC1);
    list.add(sC2);
    list.add(sC3);
    list.add(sC4);

    // this one would manage without the equals method,
    // its found by reference (address) value
    System.out.println("sC3 index: "+list.indexOf(sC3));

    // this one misses (returns -1) without the equals method.
    SomeClass sC5=new SomeClass ("GHI",323);
    System.out.println("sC5 index: "+list.indexOf(sC5));
  }
  public static void main(String[] args) {
    AList al=new AList();
  }
}