调用静态方法时的类实例

Question

What I'm trying to do is create a method that can find the midpoint between two points. Also I'm trying to have the quadrant of these midpoints displayed. The problem is that it doesn't correctly set the quadrant again after changing the coordinates to the midpoint and before displaying the point. Here's my code:

public class OrderedPairTest {


    public static void main(String[] args) {
        OrderedPair op1 = new OrderedPair(0,0);
        OrderedPair op2 = new OrderedPair(0,0);
        OrderedPair op3 = new OrderedPair(0,0);
        System.out.println(op1.a);
        System.out.println(op1.b);
        System.out.println(op1.setX(2));
        System.out.println(op1.setY(3));
        System.out.println(op2.moveX(-1));
        System.out.println(op2.moveY(-3));
        System.out.println(op3.moveXY(-4,4));
        System.out.println(op1.printOP());
        System.out.println(op2.printOP());
        System.out.println(op3.printOP());
        System.out.println(op1.distance(op2));
        System.out.println(op1.distance(op3));
        System.out.println("The distance between the two points is: "+op1.distancestat(op2,op3));
        System.out.println("The midpoint is at: "+op1.midpoint(op2)+op2.q);
        System.out.println("The midpoint is at: "+op2.midpointstat(op1,op3)+op2.q);     
    }
}   

public class OrderedPair {
    int a,b;
    public OrderedPair(int x,int y){
        a = x;
        b = y;
    }
    String q = "";
    String msg = "";
    String error = "";
    String result = "";
    public int getX() {                                                                                 //Gets the value of X
        result = "X is "+a+".";
        return a;
    }
    public int getY() {                                                                                 //Gets the value of Y
        result = "Y is "+b+".";
        return b;   
    }
    public String setX(int x) {                                                                         //Sets the value of X
        a = x;
        result = "X has been set to "+a;        
        if (b != 0) setQ();
        else;
        return result;  
    }
    public String setY(int y) {                                                                         //Sets the value of Y
        b = y;
        result = "Y has been set to "+b;        
        if (a != 0) setQ();
        else;
        return result;  
    }        
    public String toString() {                                                                          //Turns the variables into a string
        msg = ("("+a+","+b+") Q"+q);
        result = "Values have been converted into string.";
        return msg;     
    }
    public String moveX(int amt) {                                                                          //Moves X a predefined amount of units
        a+=amt;
        result = "X has been moved "+amt+" units.";     
        if ((b != 0) && (a != 0)) setQ();
        else;   
        return result;  
    }
    public String moveY(int amt) {                                                                          //Moves Y a predefined amount of units
        b+=amt;
        result = "Y has been moved "+amt+" units."; 
        if ((b != 0) && (a != 0)) setQ();
        else;
        return result;          
    }
    public String moveXY(int amt1, int amt2){                                                               //Moves X and Y a predefined amount of units
        a+=amt1;
        b+=amt2;
        result = "X has been moved "+amt1+" units.Y has been moved "+amt2+" units.";
        if ((b != 0) && (a != 0)) setQ();
        else;
        return result;
    }
    public String distance(OrderedPair other) {                                                         //Gets the distance between two pairs of choordinates
        double d = Math.sqrt(Math.pow(other.b-this.b,2)+Math.pow(other.a-this.a,2));
        result = "The distance between the two points is: "+d;
        return result;
    }
    public static double distancestat(OrderedPair other1, OrderedPair other2) {                                 //Gets the distance between two pairs of static choordinates
        double d = Math.sqrt(Math.pow(other1.b-other2.b,2)+Math.pow(other1.a-other1.b,2));
        return d;
    }
    public OrderedPair midpoint(OrderedPair other) {                                                            //Gets the midpoint between two pairs of choordinates
        return new OrderedPair((this.getX()+other.getX())/2,(this.getY()+other.getY())/2);          
    }
    public static OrderedPair midpointstat(OrderedPair other1, OrderedPair other2) {                                                                                                //Gets the midpoint between two pairs of static choordinates
        return new OrderedPair((other1.getX()+other2.getX())/2,(other1.getY()+other2.getY())/2);        
    }    
    public String printOP() {                                                                               //Calls toString() then prints the string set by toString()
        toString();
        if (q!= "") return msg;
        else error = "Q has not been set.";
        return error;
    } 
    private String setQ() {                                                                             //Sets the quadrant based on the signs of the choordinates
        if ((a!=0)&&(b!=0)){
            if (a > 0){
                if (b > 0) q = "I";     
                else q = "IV";
            }
            else {
                if (b > 0) q = "II";
                else q = "III";
            }       
            result = "The quadrant has been set.";
            return result;
        }
        else error = "X and/or Y are zero, please assign the variables a nonzero value.";
        return error;   
    }            
}

Answer 1

1. Dividing by 2 instead of 2.0 in your midpoint calculation is problematic.

2. Whether in setX(), setY() or setQ(), correctly handle the condition where a or b equals zero with if a==0 or b==0 then q = ""

3. In distancestat() should be

double d = Math.sqrt(Math.pow(other1.b-other2.b,2)+Math.pow(other1.a-other2.a,2)); // change is at the end - other2.a

vice

double d = Math.sqrt(Math.pow(other1.b-other2.b,2)+Math.pow(other1.a-other1.b,2));