Programming Forums > Application Development > Java

jch02140 · Aug 14th, 2005, 1:08 AM

I am trying to write a code using recursive method to check if a sorted list contains a given index. However, I receive compile errors when trying to compile the code.

Errors Received:

1. asList(java.lang.Object[]) in java.util.Arrays cannot be applied to (int[])

2. non-static variable cannot be referenced from a static context.

3. cannot resolve symbol method contains(java.util.List,int)

What is wrong?...

(Toggle Plain Text)

import java.io.*;
import java.util.*;

public class NumberTest
{
	private int values[] = {2,4,7,9,10,14,16,17,20,26,28,32,40};
    private List aList = new ArrayList(Arrays.asList(values);
	
	public static boolean contains(List aList, Integer anInteger)
	{
		if (aList.size() == 0) return false;
		return contains(aList, anInteger, 0, aList.size()-1);
	}
	
	public static boolean contains(List aList, Integer anInteger, int beginIndex, int endIndex)
	{
		if (beginIndex == endIndex)
			return aList.get(beginIndex).equals(anInteger);
		
		if (anInteger.intValue()<((Integer)aList.get(beginIndex)).intValue())
			return false;
		
		if (anInteger.intValue()>((Integer)aList.get(beginIndex)).intValue())
			return false;
		
		int middleIndex = (endIndex + beginIndex)/2;
		Integer middleInteger = (Integer)aList.get(middleIndex);
		
		if (anInteger.intValue() < middleInteger.intValue())
			return contains(aList,anInteger,beginIndex,middleIndex);
			
		return contains(aList,anInteger,middleIndex+1, endIndex);
	}
	
	public static void main(String args[])
	{
		System.out.print(contains(aList,16));
		
	}
}

OpenLoop · Aug 14th, 2005, 1:26 PM

I'm new to java but in one of the tutorials i'm studying, it says that ArrayList has to have Objects as parameters and not primitive types. You can use type wrappers (Integer instead of int) but i don't know how to manipulate'em yet. Here's the definition for an Integer array of object:

(Toggle Plain Text)

private Integer[] values = new Integer[13];
//now you need to get these values into the new array:{2,4,7,9,10,14,16,17,20,26,28,32,40};
// I'm not sure how to do this

stevengs · Aug 14th, 2005, 1:30 PM

.. the wrapper's methods simply call the wrapped class's methods (seems kinda pointless though

)

OpenLoop · Aug 14th, 2005, 1:37 PM

Quote:

Originally Posted by stevengs

.. the wrapper methods simply need to call the wrapped class's methods (seems kinda pointless though

)

well, i also read that the conversion takes place automatically in JDK 5.0 so you don't have to deal with all this none sense.

jch02140 · Aug 14th, 2005, 2:38 PM

I have changed the code but I still get an error message when I compile it

(Toggle Plain Text)

import java.io.*;
import java.util.*;
 
public class NumberTest
{
	private static int[] values = {2,4,7,9,10,14,16,17,20,26,28,32,40};
    private static List aList;
	
	public static boolean contains(List aList, Integer anInteger)
	{
	    initList();
	    
		if (aList.size() == 0) return false;
		return contains(aList, anInteger, 0, aList.size()-1);
	}
	
	public static boolean contains(List aList, Integer anInteger, int beginIndex, int endIndex)
	{
	    initList();
	    
		if (beginIndex == endIndex)
			return aList.get(beginIndex).equals(anInteger);
		
		if (anInteger.intValue()<((Integer)aList.get(beginIndex)).intValue())
			return false;
		
		if (anInteger.intValue()>((Integer)aList.get(beginIndex)).intValue())
			return false;
		
		int middleIndex = (endIndex + beginIndex)/2;
		Integer middleInteger = (Integer)aList.get(middleIndex);
		
		if (anInteger.intValue() < middleInteger.intValue())
			return contains(aList,anInteger,beginIndex,middleIndex);
			
		return contains(aList,anInteger,middleIndex+1, endIndex);
	}
	
	private static void initList()
	{
	    if (aList != null)
	        return;
	    
	    Integer[] valuesObj = new Integer[values.length];
	    for (int i = 0; i < values.length; i++)
	        valuesObj[i] = new Integer(values[i]);
        aList = new ArrayList(Arrays.asList(valuesObj));        
	}
	
	public static void main(String[] args)
	{
		System.out.print(contains(aList,16));  // Cannot resolve symbol method (java.util.List, int).
		
	}
}

stevengs · Aug 14th, 2005, 2:42 PM

Quote:

Originally Posted by jch02140

I have changed the code but I still get an error message when I compile it

... hmmm.... are you just gone let the suspense build up or what? Just because we know some programmin' doesn't make us omniscient. And most of us are not psychic. Care to let us in on yer little secret?

OpenLoop · Aug 14th, 2005, 3:08 PM

I agree with stevengs, you need to be as verbose as the linux kernel so we can help you better.
Since I am in the process of learning java, I though it would be a good practice to get your code to compile, here it is:

(Toggle Plain Text)

//package numbertest;
import java.io.*;
import java.util.*;

public class NumberTest
{
     //notice the static keywords before the declarations are necessary here
    private static Integer[] values = {new Integer(2),new Integer(4), new Integer(7),
        new Integer(9),new Integer(10),new Integer(14),new Integer(16),
        new Integer(17),new Integer(20),new Integer(26),new Integer(28),
        new Integer(32),new Integer(40)};  //Array of Integer Objects
    
    private static List aList = new ArrayList(Arrays.asList(values));
    
        public static boolean contains(List aList, Integer anInteger)
        {
                if (aList.size() == 0) return false;
                return contains(aList, anInteger, 0, aList.size()-1);
        }

        public static boolean contains(List aList, Integer anInteger, int beginIndex, int endIndex)
        {
                if (beginIndex == endIndex)
                        return aList.get(beginIndex).equals(anInteger);

                if (anInteger.intValue()<((Integer)aList.get(beginIndex)).intValue())
                        return false;

                if (anInteger.intValue()>((Integer)aList.get(beginIndex)).intValue())
                        return false;

                int middleIndex = (endIndex + beginIndex)/2;
                Integer middleInteger = (Integer)aList.get(middleIndex);

                if (anInteger.intValue() < middleInteger.intValue())
                        return contains(aList,anInteger,beginIndex,middleIndex);

                return contains(aList,anInteger,middleIndex+1, endIndex);
        }

        public static void main(String args[])
        {
                System.out.print(contains(aList,new Integer(16)));
             //here, you cannot send "16" as an argument for contains(). you must create an integer object because that's how YOU defined your contains() function!
        }
}

Still, i don't know if the program is doing its job I just fixed the compile problems

Aug 14th, 2005, 1:08 AM	#1
jch02140 Newbie Join Date: Jul 2005 Posts: 15 Rep Power: 0	Problem in my Java Code I am trying to write a code using recursive method to check if a sorted list contains a given index. However, I receive compile errors when trying to compile the code. Errors Received: 1. asList(java.lang.Object[]) in java.util.Arrays cannot be applied to (int[]) 2. non-static variable cannot be referenced from a static context. 3. cannot resolve symbol method contains(java.util.List,int) What is wrong?... (Toggle Plain Text) import java.io.; import java.util.; public class NumberTest { private int values[] = {2,4,7,9,10,14,16,17,20,26,28,32,40}; private List aList = new ArrayList(Arrays.asList(values); public static boolean contains(List aList, Integer anInteger) { if (aList.size() == 0) return false; return contains(aList, anInteger, 0, aList.size()-1); } public static boolean contains(List aList, Integer anInteger, int beginIndex, int endIndex) { if (beginIndex == endIndex) return aList.get(beginIndex).equals(anInteger); if (anInteger.intValue()<((Integer)aList.get(beginIndex)).intValue()) return false; if (anInteger.intValue()>((Integer)aList.get(beginIndex)).intValue()) return false; int middleIndex = (endIndex + beginIndex)/2; Integer middleInteger = (Integer)aList.get(middleIndex); if (anInteger.intValue() < middleInteger.intValue()) return contains(aList,anInteger,beginIndex,middleIndex); return contains(aList,anInteger,middleIndex+1, endIndex); } public static void main(String args[]) { System.out.print(contains(aList,16)); } } import java.io.; import java.util.; public class NumberTest { private int values[] = {2,4,7,9,10,14,16,17,20,26,28,32,40}; private List aList = new ArrayList(Arrays.asList(values); public static boolean contains(List aList, Integer anInteger) { if (aList.size() == 0) return false; return contains(aList, anInteger, 0, aList.size()-1); } public static boolean contains(List aList, Integer anInteger, int beginIndex, int endIndex) { if (beginIndex == endIndex) return aList.get(beginIndex).equals(anInteger); if (anInteger.intValue()<((Integer)aList.get(beginIndex)).intValue()) return false; if (anInteger.intValue()>((Integer)aList.get(beginIndex)).intValue()) return false; int middleIndex = (endIndex + beginIndex)/2; Integer middleInteger = (Integer)aList.get(middleIndex); if (anInteger.intValue() < middleInteger.intValue()) return contains(aList,anInteger,beginIndex,middleIndex); return contains(aList,anInteger,middleIndex+1, endIndex); } public static void main(String args[]) { System.out.print(contains(aList,16)); } }

Aug 14th, 2005, 1:26 PM	#2
OpenLoop Expert Programmer Join Date: May 2005 Location: East Lansing, MI Posts: 663 Rep Power: 4	I'm new to java but in one of the tutorials i'm studying, it says that ArrayList has to have Objects as parameters and not primitive types. You can use type wrappers (Integer instead of int) but i don't know how to manipulate'em yet. Here's the definition for an Integer array of object: (Toggle Plain Text) private Integer[] values = new Integer[13]; //now you need to get these values into the new array:{2,4,7,9,10,14,16,17,20,26,28,32,40}; // I'm not sure how to do this private Integer[] values = new Integer[13]; //now you need to get these values into the new array:{2,4,7,9,10,14,16,17,20,26,28,32,40}; // I'm not sure how to do this

Aug 14th, 2005, 1:30 PM	#3
stevengs Professional Programmer Join Date: May 2005 Location: Bad Nauheim, Germany Posts: 436 Rep Power: 4	.. the wrapper's methods simply call the wrapped class's methods (seems kinda pointless though ) __________________ -Steven "Is this a piece of your brain?" - Basil Fawlty

Aug 14th, 2005, 2:38 PM	#5
jch02140 Newbie Join Date: Jul 2005 Posts: 15 Rep Power: 0	I have changed the code but I still get an error message when I compile it (Toggle Plain Text) import java.io.; import java.util.; public class NumberTest { private static int[] values = {2,4,7,9,10,14,16,17,20,26,28,32,40}; private static List aList; public static boolean contains(List aList, Integer anInteger) { initList(); if (aList.size() == 0) return false; return contains(aList, anInteger, 0, aList.size()-1); } public static boolean contains(List aList, Integer anInteger, int beginIndex, int endIndex) { initList(); if (beginIndex == endIndex) return aList.get(beginIndex).equals(anInteger); if (anInteger.intValue()<((Integer)aList.get(beginIndex)).intValue()) return false; if (anInteger.intValue()>((Integer)aList.get(beginIndex)).intValue()) return false; int middleIndex = (endIndex + beginIndex)/2; Integer middleInteger = (Integer)aList.get(middleIndex); if (anInteger.intValue() < middleInteger.intValue()) return contains(aList,anInteger,beginIndex,middleIndex); return contains(aList,anInteger,middleIndex+1, endIndex); } private static void initList() { if (aList != null) return; Integer[] valuesObj = new Integer[values.length]; for (int i = 0; i < values.length; i++) valuesObj[i] = new Integer(values[i]); aList = new ArrayList(Arrays.asList(valuesObj)); } public static void main(String[] args) { System.out.print(contains(aList,16)); // Cannot resolve symbol method (java.util.List, int). } } import java.io.; import java.util.; public class NumberTest { private static int[] values = {2,4,7,9,10,14,16,17,20,26,28,32,40}; private static List aList; public static boolean contains(List aList, Integer anInteger) { initList(); if (aList.size() == 0) return false; return contains(aList, anInteger, 0, aList.size()-1); } public static boolean contains(List aList, Integer anInteger, int beginIndex, int endIndex) { initList(); if (beginIndex == endIndex) return aList.get(beginIndex).equals(anInteger); if (anInteger.intValue()<((Integer)aList.get(beginIndex)).intValue()) return false; if (anInteger.intValue()>((Integer)aList.get(beginIndex)).intValue()) return false; int middleIndex = (endIndex + beginIndex)/2; Integer middleInteger = (Integer)aList.get(middleIndex); if (anInteger.intValue() < middleInteger.intValue()) return contains(aList,anInteger,beginIndex,middleIndex); return contains(aList,anInteger,middleIndex+1, endIndex); } private static void initList() { if (aList != null) return; Integer[] valuesObj = new Integer[values.length]; for (int i = 0; i < values.length; i++) valuesObj[i] = new Integer(values[i]); aList = new ArrayList(Arrays.asList(valuesObj)); } public static void main(String[] args) { System.out.print(contains(aList,16)); // Cannot resolve symbol method (java.util.List, int). } }

Aug 14th, 2005, 3:08 PM	#7
OpenLoop Expert Programmer Join Date: May 2005 Location: East Lansing, MI Posts: 663 Rep Power: 4	I agree with stevengs, you need to be as verbose as the linux kernel so we can help you better. Since I am in the process of learning java, I though it would be a good practice to get your code to compile, here it is: (Toggle Plain Text) //package numbertest; import java.io.; import java.util.; public class NumberTest { //notice the static keywords before the declarations are necessary here private static Integer[] values = {new Integer(2),new Integer(4), new Integer(7), new Integer(9),new Integer(10),new Integer(14),new Integer(16), new Integer(17),new Integer(20),new Integer(26),new Integer(28), new Integer(32),new Integer(40)}; //Array of Integer Objects private static List aList = new ArrayList(Arrays.asList(values)); public static boolean contains(List aList, Integer anInteger) { if (aList.size() == 0) return false; return contains(aList, anInteger, 0, aList.size()-1); } public static boolean contains(List aList, Integer anInteger, int beginIndex, int endIndex) { if (beginIndex == endIndex) return aList.get(beginIndex).equals(anInteger); if (anInteger.intValue()<((Integer)aList.get(beginIndex)).intValue()) return false; if (anInteger.intValue()>((Integer)aList.get(beginIndex)).intValue()) return false; int middleIndex = (endIndex + beginIndex)/2; Integer middleInteger = (Integer)aList.get(middleIndex); if (anInteger.intValue() < middleInteger.intValue()) return contains(aList,anInteger,beginIndex,middleIndex); return contains(aList,anInteger,middleIndex+1, endIndex); } public static void main(String args[]) { System.out.print(contains(aList,new Integer(16))); //here, you cannot send "16" as an argument for contains(). you must create an integer object because that's how YOU defined your contains() function! } } //package numbertest; import java.io.; import java.util.; public class NumberTest { //notice the static keywords before the declarations are necessary here private static Integer[] values = {new Integer(2),new Integer(4), new Integer(7), new Integer(9),new Integer(10),new Integer(14),new Integer(16), new Integer(17),new Integer(20),new Integer(26),new Integer(28), new Integer(32),new Integer(40)}; //Array of Integer Objects private static List aList = new ArrayList(Arrays.asList(values)); public static boolean contains(List aList, Integer anInteger) { if (aList.size() == 0) return false; return contains(aList, anInteger, 0, aList.size()-1); } public static boolean contains(List aList, Integer anInteger, int beginIndex, int endIndex) { if (beginIndex == endIndex) return aList.get(beginIndex).equals(anInteger); if (anInteger.intValue()<((Integer)aList.get(beginIndex)).intValue()) return false; if (anInteger.intValue()>((Integer)aList.get(beginIndex)).intValue()) return false; int middleIndex = (endIndex + beginIndex)/2; Integer middleInteger = (Integer)aList.get(middleIndex); if (anInteger.intValue() < middleInteger.intValue()) return contains(aList,anInteger,beginIndex,middleIndex); return contains(aList,anInteger,middleIndex+1, endIndex); } public static void main(String args[]) { System.out.print(contains(aList,new Integer(16))); //here, you cannot send "16" as an argument for contains(). you must create an integer object because that's how YOU defined your contains() function! } } Still, i don't know if the program is doing its job I just fixed the compile problems

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Programming Forums > Application Development > Java

Problem in my Java Code