Problem on Generic example from K&B study guide

[Chidimma Juliana]

Please could someone help ,

I tried to compile the program below but it fails;

import java.util.*;
   public class TestLegacy{
     public static void main(String [] args){
       List<Integer> myList = new ArrayList<Integer>();
    
       myList.add(4);
       myList.add(6);
       Adder adder = new Adder();
       int total = adder.addAll(myList);
       System.out.println(total);
   }
}

What could be the problem?

Thank you

[Stephan van Hulst]

We won't know, unless you post the error, and the Adder class.

[Chidimma Juliana]

Hello Stephan,

Am sorry providing incomplete information.

import java.util.*;
   
class Adder{
  int addAll(List list){
    Iterator it =  List.iterator();
    int total = 0;
    while(it.hasNext()){
    int i = ((Integer)it.next()).intValue();
    total += i;
    }
  return total;
  }
}

public class TestLegacy{
     public static void main(String [] args){
       List<Integer> myList = new ArrayList<Integer>();
    
       myList.add(4);
       myList.add(6);
       Adder adder = new Adder();
       int total = adder.addAll(myList);
       System.out.println(total);
     }
}

Below is compiler error message.

C:\Documents and Settings\Chidimma\Desktop\Allfiles>javac TestLegacy.java
TestLegacy.java:5: non-static method iterator() cannot be referenced from a stat
ic context
Iterator it = List.iterator();
^
TestLegacy.java:8: cannot find symbol
symbol : method intValue()
location: class Integer
int i = ((Integer)it.next()).intValue();
^
TestLegacy.java:19: cannot find symbol
symbol : method add(int)
location: interface java.util.List<Integer>
myList.add(4);
^
TestLegacy.java:20: cannot find symbol
symbol : method add(int)
location: interface java.util.List<Integer>
myList.add(6);
^
.\Integer.java:9: cannot find symbol
symbol : constructor Integer()
location: class Integer
Integer y = new Integer();
^
.\Integer.java:11: cannot find symbol
symbol : method intValue()
location: class Integer
int x = y.intValue();




Thank you

[ayatullah syauqi qasthalani]

Iterator it = List.iterator();

it should be :
Iterator it = list.iterator();

[Chidimma Juliana]

I have corrected List to list which was used to invoke the iterator method. But the compilation still fails.

import java.util.*;
  
class Adder{
  int addAll(List list){
    Iterator it =  list.iterator();
    int total = 0;
    while(it.hasNext()){
    int i = ((Integer)it.next()).intValue();
    total += i;
    }
  return total;
  }
}

public class TestLegacy{
     public static void main(String [] args){
       List<Integer> myList = new ArrayList<Integer>();
    
       myList.add(4);
       myList.add(6);
       Adder adder = new Adder();
       int total = adder.addAll(myList);
       System.out.println(total);
     }
}

[John Schubert]

It compiles fine on my machine.

[Pranav Raulkar]

Compiles and runs fine on my machine too.

I guess you are not using any IDE to run this. I copied the code into Eclipse and changed compiler compliance level. I can see that 1.6 and 1.5 work just fine, but setting it to 1.4 shows problem in Eclipse for Integer.

[Chidimma Juliana]

Hello,

Am using command prompt and compiler is jdk, below is the version of the compiler;

C:\Documents and Settings\Chidimma\Desktop\Allfiles>javac -version
javac 1.6.0_26

[Arjun Srivastava]

Chidimma Juliana wrote:
C:\Documents and Settings\Chidimma\Desktop\Allfiles>javac -version
javac 1.6.0_26

It works even on command prompt.Your version is also valid.