1.类图：

2.结果：

3.代码及界面：

1 package test; 2 public class Triangle {     3     public String triangle(int a,int b,int c){ 4         String str=null; 5         if(a+b>c){ 6             if((a == b)||(b == c)&&(a!=c)) 7             { 8                 str = "等腰三角形"; 9             }10             else if(a == b&& b== c)11             {12                 str = "等边三角形";13             }else if(a*a+b*b==c*c){14                 str = "直角三角形";15             }else16                 str="一般三角形";    17             }18             else {19                 str = "不构成三角形";20             }21             return str;22     }23     public float triangleArea(int a,int b,int c){24         float p=(a+b+c)/2;25         float s=(float)Math.sqrt(p*(p-a)*(p-b)*(p-c));26         return s;27     }    28     public  int Perimeter(int a,int b,int c){29         return a+b+c;30     }31 }

界面代码：

1 package test;  2   3 import java.awt.EventQueue;  4 import java.awt.event.ActionEvent;  5 import java.awt.event.ActionListener;  6 import javax.swing.JFrame;  7 import javax.swing.JLabel;  8 import javax.swing.JOptionPane;  9 import javax.swing.JTextField; 10 import javax.swing.JButton; 11 import java.awt.event.WindowEvent;  12 import java.util.Arrays; 13 import java.awt.event.WindowAdapter;  14  15 public class FrameTriangle { 16     private JFrame frame = new JFrame("三角形计算程序"); 17     private JButton b1 = new JButton("OK"); 18     private JButton b2 = new JButton("Cancel"); 19     private JLabel lab1 = new JLabel("请输入三角形的三条边："); 20     private JLabel length1 = new JLabel("a:"); 21     private JLabel length2 = new JLabel("b:"); 22     private JLabel length3 = new JLabel("c:"); 23     private JLabel define = new JLabel("这个三角形是："); 24     private JLabel area = new JLabel("面积是:"); 25     private JLabel perimeter = new JLabel("周长是:"); 26     private JTextField a = new JTextField(); 27     private JTextField b = new JTextField(); 28     private JTextField c = new JTextField(); 29     private JTextField judge = new JTextField(); 30     private JTextField s = new JTextField(); 31     private JTextField per = new JTextField(); 32     Triangle t=new Triangle(); 33     public FrameTriangle(){ 34         b1.addActionListener(new ActionListener(){ 35         @Override 36             public void actionPerformed(ActionEvent e){ 37                 try{ 38                     int[] num; 39                     num = new int[3]; 40                     num[0]=Integer.parseInt(a.getText()); 41                     num[1]=Integer.parseInt(b.getText()); 42                     num[2]=Integer.parseInt(c.getText()); 43                     if(num[0]>100||num[0]<1||num[1]>100||num[1]<1||num[2]>100||num[2]<1){ 44                         JOptionPane.showMessageDialog(null,"边的值不在范围内"); 45                         return; 46                     } 47                     Arrays.sort(num); 48                     judge.setText(t.triangle(num[0],num[1],num[2])); 49                     s.setText(""+t.triangleArea(num[0],num[1],num[2])); 50                     per.setText(""+t.Perimeter(num[0],num[1],num[2])); 51                 }catch(Exception ex){ 52                     JOptionPane.showMessageDialog(null,"请输入整数"); 53                  } 54            } 55        }); 56        b2.addActionListener(new ActionListener(){ 57            @Override 58            public void actionPerformed(ActionEvent e) { 59            a.setText(""); 60            b.setText(""); 61            c.setText(""); 62            judge.setText(""); 63            s.setText(""); 64            per.setText(""); 65        }}); 66        frame.addWindowListener(new WindowAdapter(){ 67            public void windowClosing(WindowEvent e){ 68                System.exit(1); 69            } 70        }); 71        frame.setLayout(null); 72        lab1.setBounds(55,10,350,30); 73        length1.setBounds(55,60,30,15); 74        length2.setBounds(145,60,30,15); 75        length3.setBounds(225,60,30,15); 76        define.setBounds(55,130,300,30); 77        area.setBounds(55,180,50,20); 78        perimeter.setBounds(180,180,50,20); 79        a.setBounds(70,55,50,25); 80        b.setBounds(160,55,50,25); 81        c.setBounds(240,55,50,25); 82        judge.setBounds(140,130,150,30); 83        s.setBounds(100,180,55,25); 84        per.setBounds(230,180,55,25); 85        b1.setBounds(55,90,100,30); 86        b2.setBounds(175,90,100,30); 87        frame.add(lab1); 88        frame.add(length1); 89        frame.add(length2); 90        frame.add(length3); 91        frame.add(define); 92        frame.add(area); 93        frame.add(perimeter); 94        frame.add(a); 95        frame.add(b); 96        frame.add(c); 97        frame.add(judge); 98        frame.add(s); 99        frame.add(per);100        frame.add(b1);101        frame.add(b2);102        frame.setSize(500,400);103        frame.setVisible(true);    104     }                 105     public static void main(String[] args){106         EventQueue.invokeLater(new Runnable() {107             public void run() {108                 try{109                     FrameTriangle window = new FrameTriangle();110                     window.frame.setVisible(true);111                     }catch (Exception e){112                         e.printStackTrace();113                      }114             }115         });116     }    117 }