operator && cannot be applied to boolean,int - error

[Linda Selfridge]

So I am compling a program that is due tonight and I cannot get past these errors.....

I really need help on this one!

//This program is designed to update the position of a point within a square.

import java.util.Scanner;

public class Point
{
	public static void main (String [] args)
	{
		
	Scanner keyboard = new Scanner (System.in);

	int direction;	//direction of point
	int x = 0;		// x coordinate
	int y = 0;		// y coordinate
	int left;		// left direction
	int Left;		// left direction
	int right;		// right direction
	int Right;		// right direction
	int down;		// down direction
	int Down;		// down direction
	int up;		// up direction
	int Up;		// up direction
	int invalidEntry;	// invalid user input
	int moves;		// number of total moves

	System.out.print("This program updates the position of a traveling point in a square");
	System.out.print("Starting position of the point is (0,0)");
	System.out.print("Enter a direction for the point to move (up, down, left or right): ");
		direction = keyboard.nextint();

	invalidEntry = (direction != left && Left && right && Right && down && Down && up && Up)
	moves = ++counter;
	if (direction == left && Left) {
		then (x = x - 1);
		System.out.println("Position of the point is now ((x),(y))");
		}else if (direction == right && Right) {
		then (x = x + 1);
		System.out.println("Position of the point is now ((x),(y))");
		}else if (direction == down && Down) {
		then (y = y - 1);
		System.out.println("Position of the point is now ((x),(y))");
		}else if (direction == up && Up) {
		then (y = y + 1);
		System.out.println("Position of the point is now ((x),(y))");
		}else {
		then ((invalidEntry));
		}
	if ((x < 4 && x < -4) && (y < 4 && y < -4)) {
		do {
		System.out.print("Enter a new direction (up, down, left or right): ");
		} while ((x == 4 && x == -4) && (y == 4 && y == -4)); {
		System.out.print("The point has reached the boundary at ((x),(y)) after +(moves) moves");
		}
		}
	}
}

I keep getting the following errors....

Main.java:29: cannot find symbol
symbol : method nextint()
location: class java.util.Scanner
direction = keyboard.nextint();
^
Main.java:31: operator && cannot be applied to boolean,int
invalidEntry = (direction != left && Left && right && Right && down && Down && up && Up)
^
Main.java:32: cannot find symbol
symbol : variable counter
location: class Point
moves = ++counter;
^
Main.java:33: operator && cannot be applied to boolean,int
if (direction == left && Left) {
^
Main.java:34: cannot find symbol
symbol : method then(int)
location: class Point
then (x = x - 1);
^
Main.java:36: operator && cannot be applied to boolean,int
}else if (direction == right && Right) {
^
Main.java:37: cannot find symbol
symbol : method then(int)
location: class Point
then (x = x + 1);
^
Main.java:39: operator && cannot be applied to boolean,int
}else if (direction == down && Down) {
^
Main.java:40: cannot find symbol
symbol : method then(int)
location: class Point
then (y = y - 1);
^
Main.java:42: operator && cannot be applied to boolean,int
}else if (direction == up && Up) {
^
Main.java:43: cannot find symbol
symbol : method then(int)
location: class Point
then (y = y + 1);
^
Main.java:46: cannot find symbol
symbol : method then(int)
location: class Point
then ((invalidEntry));
^

Can anyone help me PLEASE!!! Desperate! I am having to use an online complier at the moment as I cannot access the remote one I am supposed to use for school.

Thanking everyone in advance!!!

[Rahul Sudip Bose]

Main.java:29: cannot find symbol
symbol : method nextint()
location: class java.util.Scanner
direction = keyboard.nextint(); 

this tells you that there is no method called nextint(). Right, change it to nextInt();
When you have doubts about names, properties of a class look in oracle/sun docs online. This is just 1 error less, more remain.

PS : what is this code trying to do ? please describe it for ease of understanding.

[Rahul Sudip Bose]

Main.java:31: operator && cannot be applied to boolean,int
invalidEntry = (direction != left && Left && right && Right && down && Down && up && Up)
^

&& can only take boolean values ie, anything that can be true or false. Nothing else is allowed. Why are you giving it ints ?
M&&N means both M and N must evaluate to a boolean. eg. M can be (4>5) which is false. So the part after && is not evaluated. Since , && is a short-circuit operator(google it!).

PS : I would suggest that you refer your textbook for such theory. Which one do you use ?

[Ernie Mcracken]

Surely you need to initiliaze your left and right ints, or your direction will never equal them, and you probably want to use the logical or operator || instead of &&.

[Linda Selfridge]

Hi,

My task is to write a program that calculates and displays a position of a point inside a square. Position of a point in the plane is specified by its coordinates, two numbers: x and y, often written as a pair (x,y). The position of the point is repeatedly changed by the user who enters a direction for the point to move: up, down, left or right. Then one of the point's coordinates, x or y, will increase or decrease by one unit. Initially the point lies at (0,0) which is the centre of a square whose sides are 8 units long. If the user enters 'l' (for left) or 'r' (for right) then the first coordinate, x, will decrement or increment, respectively. Similarly, the second coordinate, y, will increment or decrement if the user enters 'u' (for up) or 'd' (for down).

I am an external student and am using "Starting out with Java", trust me it is not my best subject.

I have done some more work and changed things around and now only have 8 errors but they are all on the same line!

//This program is designed to update the position of a point within a square.
 
import java.util.Scanner;
 
public class Point
{
        public static void main (String [] args)
        {
                
        Scanner keyboard = new Scanner (System.in);
 
        double direction;       //direction of point
        double x = 0;           // x coordinate
        double y = 0;           // y coordinate
        double l;               // left direction
        double L;               // left direction
        double r;               // right direction
        double R;               // right direction
        double d;               // down direction
        double D;               // down direction
        double u;               // up direction
        double U;               // up direction
        double invalidEntry;    // invalid user input
        double moves;           // number of total moves
        double counter; // loop move counter
 
        System.out.print("This program updates the position of a traveling point in a square");
        System.out.print("Starting position of the point is (0,0)");
        System.out.print("Enter a direction for the point to move (u, d, l or r): ");
                direction = keyboard.nextDouble();
 
        invalidEntry = (direction != l & L & r & R & d & D & u & U)
        moves = ++counter;
        if (direction == l & L) {
                x = x - 1;
                System.out.println("Position of the point is now ((x),(y))");
                }else if (direction == r & R) {
                x = x + 1;
                System.out.println("Position of the point is now ((x),(y))");
                }else if (direction == d & D) {
                y = y - 1;
                System.out.println("Position of the point is now ((x),(y))");
                }else if (direction == u & U) {
                y = y + 1;
                System.out.println("Position of the point is now ((x),(y))");
                }else {
                invalidEntry = (direction != l & L & r & R & d & D & u & U);
                System.out.println(“Invalid entry, try again”);
                }
        if ((x < 4 && x < -4) && (y < 4 && y < -4)) {
                do {
                System.out.print("Enter a new direction (u, d, l or r): ");
                } while ((x == 4 && x == -4) && (y == 4 && y == -4)); {
                System.out.print("The point has reached the boundary at ((x),(y)) after +(moves) moves");
                }
                }
        }
}
}

[Linda Selfridge]

The error is on line 48 and basically revolves around the try

Main.java:48: illegal character: \8220
System.out.print(“Invalid entry, try again”);
^
Main.java:48: ';' expected
System.out.print(“Invalid entry, try again”);
^
Main.java:48: not a statement
System.out.print(“Invalid entry, try again”);
^
Main.java:48: ';' expected
System.out.print(“Invalid entry, try again”);
^
Main.java:48: '{' expected
System.out.print(“Invalid entry, try again”);
^
Main.java:48: illegal character: \8221
System.out.print(“Invalid entry, try again”);
^
Main.java:48: not a statement
System.out.print(“Invalid entry, try again”);
^
Main.java:48: 'try' without 'catch' or 'finally'
System.out.print(“Invalid entry, try again”);
^
8 errors

Thanks

[Ulf Dittmer]

The double quotes on that line don't look like regular double quotes but rather like fancy ones a word processor might use. Java does not recognize those.

[Greg Brannon]

Ulf Dittmer wrote:The double quotes on that line don't look like regular double quotes but rather like fancy ones a word processor might use. Java does not recognize those.

Good eyes!