蚀给令牌上的错误

Question

I was writing a basic program on 2d array, just defining and initializing.

 1  package testing;
 2
 3  public class Array2 {
 4    int [][] twoDim = new int[4][];
 5    twoDim[0] = new int[]{1,2,3};
 6    System.out.println(twoDim[0][1]) ;
 7  }

But I get error on line 3 at the semicolon saying that:

Syntax error on token ";", { expected after this token

What's wrong?

Answer 1

You need to put your code into somewhere it can be executed. System.out.println is an execution statement. You're probably looking to use the main method.

public class Array2 {
    public static void main(String[] args){
        int [][] twoDim = new int[4][];
        twoDim[0] = new int[]{1,2,3};
        System.out.println(twoDim[0][1]) ;
    }
}

Note: You could utilize a combination of: methods, constructors, static initializers, class declarations, etc. to make this properly execute. The main method seemed the most appropriate for what you're trying to do.

---

To answer your question in the comments of "How can I make the array a class variable".

You can make twoDim a class variable. I would use a Constructor to set the values inside the array. In your main method you would have to create an instance of your class so that you can access its members. Also note that the constructor is called when creating an instance of the class. For example:

public class Array2 {
    public int [][] twoDim = new int[4][];

    public Array2(){ // Constructor for Array2 class
        twoDim[0] = new int[]{1,2,3}; // Set the values
    }

    public static void main(String[] args){
        Array2 array2Instance = new Array2(); // Create an instance, calls constructor
        System.out.println(array2Instance.twoDim[0][1]); // Access the instance's array
    }
}

Note that you have to make the twoDim variable public in order to access it outside of the class - for instance in the main method.

Answer 2

you cannot write

System.out.println(twoDim[0][1]);

outside a method or block in java This probably should do the job

public static void main(String arr[])
{
    int [][] twoDim = new int[4][];
    twoDim[0] = new int[]{1,2,3};
    System.out.println(twoDim[0][1]) ;

}

or something like this

int [][] twoDim = new int[4][];
public void display()
{
    twoDim[0] = new int[]{1,2,3};
    System.out.println(twoDim[0][1]) ;
}


public static void main(String arr[])
{
    new Array2().display();

}

You can initialize an array inside a method, or code block.

Answer 3

System.out.println(twoDim[0][1]) ;

This statement should be inside some block or method. You cannot have it like that lying in the class. Put it inside some block or method.

If I don't write System.out.println(....), the error still persists.

You cannot initialize elements of an array after defining it that way. You need to put the statement

twoDim[0] = new int[]{1,2,3};

inside block/method/constructor.

Same goes for any array

Eg

public class HelloWorld {
    String[] strArray =new String[10];  //all good
    strArray[0] ="str";   //same compile time error you are getting
}