java - Simple calculation returning NullPointer exception... why? -


(i'm new java please forgive ignorance).

i have simple class:

public class bill {     private string total;     private int tip;     private int people;     bill() {         total = "0";         tip=0;         people=0;     }     bill (string total, int people, int tip) {         total = total;         tip = tip;         people = people;     }      //the problem here somewhere.     private double split = (double.parsedouble(total) * ((double)tip / 100)) / (double)people;      public string gettotal() {         return total;     }      public double getsplit() {         return split;     }      public double gettip() {         return tip;     }  }

when call 'getsplit()' method, runtime crashes nullpointer exception:

09-03 19:37:02.609: e/androidruntime(11325): caused by: java.lang.nullpointerexception 09-03 19:37:02.609: e/androidruntime(11325):    @ java.lang.stringtoreal.parsedouble(stringtoreal.java:244) 09-03 19:37:02.609: e/androidruntime(11325):    @ java.lang.double.parsedouble(double.java:295) 09-03 19:37:02.609: e/androidruntime(11325):    @ williamgill.de.helloworld.bill.<init>(bill.java:21) 09-03 19:37:02.609: e/androidruntime(11325):    @ williamgill.de.helloworld.displaymessageactivity.oncreate(displaymessageactivity.java:38)

i seem doing wrong casting of types - can't life of me think what.

at time line executes

private double split = (double.parsedouble(total) * ((double)tip / 100)) / (double)people;

the fields total , others have not been initialized constructor , have default value of null. parsedouble() must throw nullpointerexception if argument null (i cannot verify this, might come dereferencing).

declare field 

private double split;

and assignment in constructor

bill (string total, int people, int tip) {     total = total;     tip = tip;     people = people;     split = (double.parsedouble(total) * ((double)tip / 100)) / (double)people; }

advice: java non-constant instance variables should start lowercase alphabetical character.


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