JAVA语言程序设计第六版编程答案第三章

3_1
import javax.swing.JOptionPane;
public class Exercise3_1{
    public static void main(String[] args){
        double edge1 = Double.parseDouble(JOptionPane.showInputDialog(null,"输入第一条边长："));
        double edge2 = Double.parseDouble(JOptionPane.showInputDialog(null,"输入第二条边长："));
        double edge3 = Double.parseDouble(JOptionPane.showInputDialog(null,"输入第三条边长："));
        boolean isTriangle = isTriangle(edge1,edge2,edge3);
        String output = "Can deges " + edge1 + " , " + edge2 + " and " + edge3 + " from a triangle? "+
        isTriangle;
        JOptionPane.showMessageDialog(null,output);
        }
    private static boolean isTriangle(double edge1,double edge2,double edge3){
        double temp;
        if(edge1<edge2){
            temp = edge1;
            edge1 = edge2;
            edge2 = temp;
            }
        if(edge1<edge3){
            temp = edge1;
            edge1 = edge3;
            edge3 = temp;
            }
        if(edge2<edge3){
            temp = edge2;
            edge2 = edge3;
            edge3 = temp;
            }
        if(edge1<(edge2+edge3))

            return true;
        else
            return false;
        }
    }
3_2
import javax.swing.JOptionPane;
public class Exercise3_2{
    public static void main(String[] args){
        int num = Integer.parseInt(JOptionPane.showInputDialog(null,"输入一个整数"));
        String output = "Is " + num + " an even number? " +isEven(num);
        JOptionPane.showMessageDialog(null,output);
        }
    private static boolean isEven(int num){
        if(num % 2 ==0)
            return true;
        else
            return false;
        }
    }
3_3
import javax.swing.JOptionPane;
public class Exercise3_3{
    public static void main(String[] args){
        int num = Integer.parseInt(JOptionPane.showInputDialog(null,"输入一个整数"));
        String output = "Is " + num + " divisible by 5 and 6 ? "+ isDivisibleBoth(num) +
            "\nIs " + num + " divisible by 5 or 6 ? "+ isDivisibleOr(num) +
            "\nIs " + num + " divisible by 5 or 6 , but not both ? "+ isDivisible(num);
        JOptionPane.showMessageDialog(null,output);
        }