Java 类将大于视为大于或等于

Question

我有一个 Java 作业，要向程序中添加 throw/catch。一切正常，除了它应该捕获任何小于 0 或大于 20 的值，它会捕获 -1 及以下或 21 及以上，但它似乎将大于视为大于或等于

类(class):

public class Rectangle {

private double width;
private double height;

public Rectangle(double width, double height) {
    setWidth(width);
    setHeight(height);
}

public void setWidth(double width) {
    if (width < 0 || width > 20) {
        throw new IllegalArgumentException("Width is not in range");
    }
    this.width = width;
}

public void setHeight(double height) {
    if (height < 0 || height > 20) {
        throw new IllegalArgumentException("Height is not in range");
    }
    this.height = height;
}

public double getWidth() {
    return width;
}

public double getHeight() {
    return height;
}

public double calculatePerimeter() {
    return 2 * (width + height);
}

public double calculateArea() {
    return width * height;
}
}

测试类:

public class RectangleTest {

public static void main(String[] args) {

    try {
        System.out.println("Enter width and length: ");
        Rectangle rectangle = new Rectangle(5, 5);
        System.out.println("Height: " + rectangle.getHeight());
        System.out.println("Width: " + rectangle.getWidth());
        System.out.println("Area: " + rectangle.calculateArea());
        System.out.println("Perimeter: " + rectangle.calculatePerimeter());
    } catch (Exception ex) {
        System.out.println(ex.getMessage());
    }
    try {
        System.out.println("Enter width and length: ");
        Rectangle rectangle = new Rectangle(25, 5);
        System.out.println("Height: " + rectangle.getHeight());
        System.out.println("Width: " + rectangle.getWidth());
        System.out.println("Area: " + rectangle.calculateArea());
        System.out.println("Perimeter: " + rectangle.calculatePerimeter());
    } catch (Exception ex) {
        System.out.println(ex.getMessage());
    }
    try {
        System.out.println("Enter width and length: ");
        Rectangle rectangle = new Rectangle(-5, 5);
        System.out.println("Height: " + rectangle.getHeight());
        System.out.println("Width: " + rectangle.getWidth());
        System.out.println("Area: " + rectangle.calculateArea());
        System.out.println("Perimeter: " + rectangle.calculatePerimeter());
    } catch (Exception ex) {
        System.out.println(ex.getMessage());
    }
    try {
        System.out.println("Enter width and length: ");
        Rectangle rectangle = new Rectangle(0, 5);
        System.out.println("Height: " + rectangle.getHeight());
        System.out.println("Width: " + rectangle.getWidth());
        System.out.println("Area: " + rectangle.calculateArea());
        System.out.println("Perimeter: " + rectangle.calculatePerimeter());
    } catch (Exception ex) {
        System.out.println(ex.getMessage());
    }
    try {
        System.out.println("Enter width and length: ");
        Rectangle rectangle = new Rectangle(5, 25);
        System.out.println("Height: " + rectangle.getHeight());
        System.out.println("Width: " + rectangle.getWidth());
        System.out.println("Area: " + rectangle.calculateArea());
        System.out.println("Perimeter: " + rectangle.calculatePerimeter());
    } catch (Exception ex) {
        System.out.println(ex.getMessage());
    }
    try {
        System.out.println("Enter width and length: ");
        Rectangle rectangle = new Rectangle(5, 0);
        System.out.println("Height: " + rectangle.getHeight());
        System.out.println("Width: " + rectangle.getWidth());
        System.out.println("Area: " + rectangle.calculateArea());
        System.out.println("Perimeter: " + rectangle.calculatePerimeter());
    } catch (Exception ex) {
        System.out.println(ex.getMessage());
    }
    try {
        System.out.println("Enter width and length: ");
        Rectangle rectangle = new Rectangle(5, -5);
        System.out.println("Height: " + rectangle.getHeight());
        System.out.println("Width: " + rectangle.getWidth());
        System.out.println("Area: " + rectangle.calculateArea());
        System.out.println("Perimeter: " + rectangle.calculatePerimeter());
    } catch (Exception ex) {
        System.out.println(ex.getMessage());
    }
    try {
        System.out.println("Enter width and length: ");
        Rectangle rectangle = new Rectangle(20,0);
        System.out.println("Height: " + rectangle.getHeight());
        System.out.println("Width: " + rectangle.getWidth());
        System.out.println("Area: " + rectangle.calculateArea());
        System.out.println("Perimeter: " + rectangle.calculatePerimeter());
    } catch (Exception ex) {
        System.out.println(ex.getMessage());
    }
}
}

为什么它将 0 和 20 视为有效值？

Answer 1

根据您的代码:

if(width < 0 || width > 20)

表示如果宽度= 0:

width < 0 = false 
width > 20 = false 

if(false || false ) => false 因为它是 OR 运算符。

如果您想检查 0 到 20 之间的值(含 0 和 20)。

您的条件应为(宽度 <= 0 ||宽度 >= 20)

如果您想专门检查 0 到 20 之间的值。

您的条件应为(宽度 < 0 || 宽度 > 20)