method overloading error in java

In Java, you cannot have multiple methods in the same class with the same method name and same argument types and count - the different return values are not considered in this context.

To resolve the issue, you must either rename one of the methods, or add or change the arguments so they're unique.

Something like this:

public Apparel getApparelById(String id)
{
    for(int i=0; i < apparel.size(); i++)
    {
        if(apparel.get(i).getId().equals(id))
        {
            return apparel.get(i);
        }
    }

    return null;
}

public ArrayList<Apparel> getApparelByName(String name)
{
    ArrayList<Apparel> apparel = new ArrayList<Apparel>();
    for(int i=0; i < this.apparel.size(); i++)
    {
        if(this.apparel.get(i).getName().equals(name))
        {
            apparel.add(this.apparel.get(i));
        }
    }

    return apparel;
}

Both methods have the same parameter types, but different return type and this is not possible. From Java Language Specification:

Two methods have the same signature if they have the same name and argument types.

If both methods has different parameter types, then it is possible.

Both of the methods getApparel(String) has the SAME METHOD SIGNATURE! JAVA and C++ DISALLOW multiple methods with the same method signature. Otherwise, the compiler wound't recognize which method is to invoke.

Method signature is identified by: method name + method parameter list(type list). Compiler doesn't differentiate methods by return type.

For detailed information you can refer to: Defining Method