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Thread: NullPointerException

  1. #1
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    Default NullPointerException

    Good evening all, I'm trying to basically enter String data into my array then int data into another matrix array and then ask the user thru swing what they want to delete from the String array, but I get the error NullPointerException as soon as I enter the word I want to delete... here's my code.. I'm not done yet but I want to know why the mistake is there..
    import javax.swing.*;
     
     
    public class TrabajoFinal
    {
    	public static void main(String[]args)
    	{
    		int opc=0;
    		do
    		{
    		String op=JOptionPane.showInputDialog(null, "1.	Ingresar nuevo municipio\n2.-Borrar un municipio\n3.Consultar información de un municipio\n4.Modificar información de un municipio\n5.Generar Reporte\n6.Salir\nQue opcion deseas?"
    		);
    		opc=Integer.parseInt(op);
    		String mun[]=new String[10];
    		int dat[][]=new int[10][10];
    		String ind[]=new String[10];
    		switch(opc)
    		{
    			case 1:IngresarMunicipio(mun, dat);break;
    			case 2:BorrarMunicipio(mun, dat);break;
    			case 3:ConsultarInfo(mun);break;
    			case 4:
    			case 5:
    			case 6:JOptionPane.showMessageDialog(null, "Adios");break;
    			default: JOptionPane.showMessageDialog(null, "Opcion invalida.");break;
    		}
    		} while(opc!=6);
    	}
     
    	public static void IngresarMunicipio(String m [], int i[][])
    	{
    		String d=(" ");
    		int cont=0;
    		for(int w=0;w<10;w++)
    		{
    		if(m[w]==null)
    		{
     
     
    		m[w]=JOptionPane.showInputDialog(null, "Cual es el nombre del municipio?");
    		JOptionPane.showMessageDialog(null, "Municipio Ingresado: "+m[w]);
     
     
    		int opc=0;
    		cont=w;
    		do
    		{
    		String op=JOptionPane.showInputDialog(null, "1.-Poblacion total\n2.-Matrimonios\n3.-Divorcios\n4.-Nacimientos\n5.-Hogares con jefatura femenina\n6.-Tasa de alfabetización de las personas de 15 a 24 años\n7.-Familias beneficiarias por el Programa de Desarrollo Humano Oportunidades\n8.-Población de 5 y más años con primaria\n9.-Población de 18 años y más con nivel profesional\n10.-Delitos registrados en averiguaciones previas del fuero común\n11.-Salir\nDame el numero de indicador que deseas cambiar/agregar._");
    		opc=Integer.parseInt(op);
    		if(opc==11)
    			JOptionPane.showMessageDialog(null, "Ingreso de datos concluidos.");
    		else
    		{
    		d=JOptionPane.showInputDialog(null, "Cual es el valor de el indicador "+opc+"?");
    		i[cont][opc-1]=Integer.parseInt(d);
    		}
    	} while(opc!=11);
    		} break;
    		}
     
    	}
     
    	public static void BorrarMunicipio(String m[], int i[][])
    	{
    		String b=JOptionPane.showInputDialog(null, "Que municipio deseas borrar?");
    		int matchIndex=-1;
     
     
    			for(int w=0;w<10;w++)
    			{
    				if(m[w].equals(b))
    				{
    					String a=JOptionPane.showInputDialog(null, "Municipio: "+m[w]+"\n"+"Indicador 1: "+i[w][0]+"\n"+"Indicador 2: "+i[w][2]+"\n"+"Indicador 3: "+i[w][2]+"\n"+"Indicador 4: "+i[w][3]+"\n"+"Indicador 5: "+i[w][4]+"\n"+"Indicador 6: "+i[w][5]+"\n"+"Indicador 7: "+i[w][6]+"\n"+"Indicador 8: "+i[w][7]+"\n"+"Indicador 9: "+i[w][8]+"\n"+"Indicador 10: "+i[w][9]+"\n"+"Estas seguro que lo quieres borrar?\n1.-SI\n2.-NO");
    					int d=Integer.parseInt(a);
    					if(d==1)
    					{
    						m[w]=(" ");
    						JOptionPane.showMessageDialog(null, "Municipio Borrado");
    						matchIndex=w;break;
    					}
    					else
    						JOptionPane.showMessageDialog(null,"Municipio no borrado.");
     
    				}
    			}
     
     
     
     
     
     
     
     
    	}
     
    	public static void ConsultarInfo(String m [])
    	{
     
    	}
    }


  2. #2
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    Default Re: NullPointerException

    Can you give us the full stack trace.

  3. #3
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    Default Re: NullPointerException

    Sorry kind of new.. what's a full stack trace?

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    Default Re: NullPointerException

    The console doesn't just say 'NullPointerException'. It will give you a much larger message called a stack trace. It will look something like this:

    Exception in thread "main" java.lang.NullPointerException
    at com.example.myproject.Book.getTitle(Book.java:16)
    at com.example.myproject.Author.getBookTitles(Author. java:25)
    at com.example.myproject.Bootstrap.main(Bootstrap.jav a:14)

  5. #5
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    Default Re: NullPointerException

    Oh right, here.
    --------------------Configuration: <Default>--------------------
    Exception in thread "main" java.lang.NullPointerException
    at TrabajoFinal.BorrarMunicipio(TrabajoFinal.java:72)
    at TrabajoFinal.main(TrabajoFinal.java:21)

  6. #6
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    Default Re: NullPointerException

    As the stackTrace says please look at line no 72 in your program or post that here. I tried copying your code but due to different editor used line no 72 is pointing to someother line where exception can't occur.

  7. #7
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    Default Re: NullPointerException

    Here's the whole method:
    Line 72 is ...
    if(m[w].equals(SearchKey))
     public static void BorrarMunicipio(String m[], int i[][])
    	{
    		String SearchKey=JOptionPane.showInputDialog(null, "Que municipio deseas borrar?");
    		int matchIndex=-1;
     
     
    			for(int w=0;w<10;w++)
    			{
    				if(m[w].equals(SearchKey))
    				{
    				matchIndex=w;
    					String a=JOptionPane.showInputDialog(null, "Municipio: "+m[w]+"\n"+"Indicador 1: "+i[w][0]+"\n"+"Indicador 2: "+i[w][1]+"\n"+"Indicador 3: "+i[w][2]+"\n"+"Indicador 4: "+i[w][3]+"\n"+"Indicador 5: "+i[w][4]+"\n"+"Indicador 6: "+i[w][5]+"\n"+"Indicador 7: "+i[w][6]+"\n"+"Indicador 8: "+i[w][7]+"\n"+"Indicador 9: "+i[w][8]+"\n"+"Indicador 10: "+i[w][9]+"\n"+"Estas seguro que lo quieres borrar?\n1.-SI\n2.-NO");
    					int d=Integer.parseInt(a);
    					if(d==1)
    					{
    						m[w]=(" ");
    						JOptionPane.showMessageDialog(null, "Municipio Borrado");
    						matchIndex=w;break;
    					}
    					else
    						JOptionPane.showMessageDialog(null,"Municipio no borrado.");
     
    				}

  8. #8
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    Default Re: NullPointerException

    Its pretty clear now that array element you try to access is null and hence it can't call equals method on null object resulting in nullpointerexception. Kindly correct the same.
    Quote Originally Posted by LuisEPB View Post
    Here's the whole method:
    Line 72 is ...

     public static void BorrarMunicipio(String m[], int i[][])
    	{
    		String SearchKey=JOptionPane.showInputDialog(null, "Que municipio deseas borrar?");
    		int matchIndex=-1;
     
     
    			for(int w=0;w<10;w++)
    			{
    				if(m[w].equals(SearchKey))
    				{
    				matchIndex=w;
    					String a=JOptionPane.showInputDialog(null, "Municipio: "+m[w]+"\n"+"Indicador 1: "+i[w][0]+"\n"+"Indicador 2: "+i[w][1]+"\n"+"Indicador 3: "+i[w][2]+"\n"+"Indicador 4: "+i[w][3]+"\n"+"Indicador 5: "+i[w][4]+"\n"+"Indicador 6: "+i[w][5]+"\n"+"Indicador 7: "+i[w][6]+"\n"+"Indicador 8: "+i[w][7]+"\n"+"Indicador 9: "+i[w][8]+"\n"+"Indicador 10: "+i[w][9]+"\n"+"Estas seguro que lo quieres borrar?\n1.-SI\n2.-NO");
    					int d=Integer.parseInt(a);
    					if(d==1)
    					{
    						m[w]=(" ");
    						JOptionPane.showMessageDialog(null, "Municipio Borrado");
    						matchIndex=w;break;
    					}
    					else
    						JOptionPane.showMessageDialog(null,"Municipio no borrado.");
     
    				}

  9. #9
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    Default Re: NullPointerException

    Found my problem!
    I was declaring my arrays inside the do-while cycle!
    So the info i was entering in my methods wasn't saving in the arrays correctly so since it had nothing to compare to it brought up the error, thank you anyway!

    --- Update ---

    Quote Originally Posted by dineshj83 View Post
    Its pretty clear now that array element you try to access is null and hence it can't call equals method on null object resulting in nullpointerexception. Kindly correct the same.
    Ok beat me to it by a few seconds.. Thanks!

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