i asked create java oop program following specifications:
student grade name : string id : string math grade : double english grade : double science grade : double average () : double printinfo () : void
the instructions are:
1)create student grade class
2)create array of 10 student
3) enter grade info using keyboard
4) print list of students (name , average)
my problem every time run public class studentgradeapp2 gives me error
exception in thread "main" java.lang.nullpointerexception @ javaday3.studentgradeapp2.main(studentgradeapp2.java:15)
now not know put on portion:
public static void printthestudentdetails (studentgrade info) { please oh please me
my codes are: studentgrade class:
package javaday3; public class studentgrade { string name; string id; double mathgrade; double enggrade; double scigrade; public void printinfo() { system.out.println("math = " + mathgrade); system.out.println("english = " + enggrade); system.out.println("science = " + scigrade); system.out.println( "average = " + average()); } public double average () { return ((mathgrade + enggrade + scigrade) / 3); } public void printcompleteinformation() { system.out.println("name = " + name); system.out.println("id = " + id); system.out.println("math = " + mathgrade); system.out.println("english = " + enggrade); system.out.println("science = " + scigrade); system.out.println( "average = " + average()); } public void printneed () { system.out.println("name = " + name); system.out.println( "average = " + average()); } } studentgradeapp class:
package javaday3; import java.util.scanner; public class studentgradeapp { public static void main(string[] args) { // todo auto-generated method stub studentgrade stud1 = new studentgrade (); stud1.name = "spongebop squarepants"; stud1.id = ("student 1"); stud1.mathgrade = 72; stud1.enggrade = 80; stud1.scigrade = 90; stud1.average(); studentgrade stud2 = new studentgrade (); stud2.name = "patrick star"; stud2.id = ("student 2 "); stud2.mathgrade = 72; stud2.enggrade = 85; stud2.scigrade = 91; stud2.average(); studentgrade stud3 = new studentgrade (); stud3.name = "squidward tentacles"; stud3.id = ("student 3" ); stud3.mathgrade = 90; stud3.enggrade = 85; stud3.scigrade = 95; stud2.average(); studentgrade stud4 = new studentgrade (); stud4.name = "eugene h. krabs"; stud4.id = ("student 4"); stud4.mathgrade = 95; stud4.enggrade = 85; stud4.scigrade = 95; stud4.average(); studentgrade stud5 = new studentgrade (); stud5.name = "sandy cheeks"; stud5.id = ("student 5"); stud5.mathgrade = 75; stud5.enggrade = 75; stud5.scigrade = 95; stud5.average(); studentgrade stud6 = new studentgrade (); stud6.name = "gary snail"; stud6.id = ("student 6"); stud6.mathgrade = 75; stud6.enggrade = 74; stud6.scigrade = 95; stud6.average(); studentgrade stud7 = new studentgrade (); stud7.name = "sheldon j plankton"; stud7.id = ("student 7 "); stud7.mathgrade = 79; stud7.enggrade = 76; stud7.scigrade = 75; stud7.average(); studentgrade stud8 = new studentgrade (); stud8.name = "larry lobster"; stud8.id = ("student 8"); stud8.mathgrade = 79; stud8.enggrade = 76; stud8.scigrade = 75; stud8.average(); studentgrade stud9 = new studentgrade (); stud9.name = "king neptune"; stud9.id = ("student 9 "); stud9.mathgrade = 79; stud9.enggrade = 96; stud9.scigrade = 75; stud9.average(); studentgrade stud10 = new studentgrade (); stud10.name = "pearl krabs"; stud10.id = ("student 10 "); stud10.mathgrade = 79; stud10.enggrade = 76; stud10.scigrade = 75; stud10.average(); /*stud1.printinfo(); system.out.println(" "); stud2.printinfo(); system.out.println(" "); stud3.printinfo(); system.out.println(" "); stud4.printinfo(); system.out.println(" "); stud5.printinfo(); system.out.println(" "); stud3.printinfo(); system.out.println(" "); stud6.printinfo(); system.out.println(" "); stud7.printinfo(); system.out.println(" "); stud8.printinfo(); system.out.println(" "); stud9.printinfo(); system.out.println(" "); stud10.printinfo(); */ } public static void printthestudentdetails (studentgrade info) { } } studentgradeapp2 class:
import java.util.scanner; public class studentgradeapp2 { public static void main(string[] args) { // todo auto-generated method stub studentgrade studgrad [] = new studentgrade [10]; scanner scanner = new scanner (system.in); for(int = 0; <= studgrad.length; i++) { system.out.print("enter math grade = "); studgrad[i].mathgrade = scanner.nextint(); system.out.print("enter english grade = "); studgrad[i].enggrade = scanner.nextint(); system.out.print("enter science grade = "); studgrad[i].scigrade = scanner.nextint(); } for(studentgrade info:studgrad) info.printinfo(); scanner.close(); } }
you have below issues posted code studentgradeapp2 :
- you got
java.lang.nullpointerexception@studgrad[i].mathgrade. equivalent invokingnull.mathgrade. mathgrade, enggrade, scigradeinstudentgradedouble , usingscanner.nextint()for loop conditionincorrect
pfb corrected implementation:
package javaday3; import java.util.scanner; public class studentgradeapp2 { public static void main(string[] args) { // todo auto-generated method stub studentgrade studgrad[] = new studentgrade[10]; scanner scanner = new scanner(system.in); (int = 0; < studgrad.length; i++) { studentgrade sg = new studentgrade(); system.out.print("enter math grade = "); sg.mathgrade = double.parsedouble(scanner.nextline()); system.out.print("enter english grade = "); sg.enggrade = double.parsedouble(scanner.nextline()); system.out.print("enter science grade = "); sg.scigrade = double.parsedouble(scanner.nextline()); studgrad[i] = sg; } (studentgrade info : studgrad) info.printinfo(); scanner.close(); } } 
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