任何人都可以帮助我解决Java中的这个错误吗？

Question

i create hash table in java but there is aproblem in it when adding elements in it.

Hashtable <Integer,String> hashT=new Hashtable<Integer ,String >();
 hashT.put<sum2 , g>;

the error in second line where define sum2 is variable contain integer value and g variable contain string value. i dont know where the problem in putting elements in hash table.i want to add the values of this variables in hash table each time as the values change.

Answer 1

To mutate an object, you have to call its properties. An object property is either a field or a method. In your case put is a method of the hashT object. A method call is done by writing the object name, then the dot operator, then the method name and finally the arguments surrounded by parenthesis:

objectName.methodName(argument1, argument2, ...);

The problem is here:

hashT.put<sum2 , g>;

put is a method and to call it you have to surround the arguments ( sum2 and g ) with parenthesis:

hashT.put(sum2, g);

Answer 2

You need to follow the comments and edit your title so its a meaningful title that will help other people understand what your question is about.

Also, when you get an error, copy the big red text that is displayed in the console (color depends on which editor you are using), also known as the error's "Stack Trace" and past it into your question somewhere. This will help us pinpoint what is going on, and the error title itself will likely give away to us exactly what's wrong.

However, without any context on what the error is and what is before or after those two lines of code it is difficult to determine if you have previously defined sum2 or g as a variable that stores values. I am going to assume you haven't assigned at least one of them, likely g as a variable.

For experimental purposes, try replacing those two lines of code with:

Hashtable <Integer,String> hashT=new Hashtable<Integer ,String >();
 hashT.put<0 , "g">;

That is putting zero ( 0 ) as an explicit integer and g as an explicit string into the hashtable. If you need to put variables into there, then you need to define them before hand, like this:

int sum2 = 3 + 4;
String g = "Some String";

Hashtable <Integer,String> hashT=new Hashtable<Integer ,String >();
hashT.put<sum2 , g>;

Now the integer value 7 is stored as the hash and the string Some String as the mapped value.