創建一個三角形類，成員變量三邊，方法求周長，創建類主類A來測試它。
1 public class sanjiaoxing {
2
3 private double a;
4 private double b;
5 private double c;
6 double zhouchang;
7
8 public double getA() {
9 return a;
10 }
11
12 public void setA(double a) {
13 this.a = a;
14 }
15
16 public double getB() {
17 return b;
18 }
19
20 public void setB(double b) {
21 this.b = b;
22 }
23
24 public double getC() {
25 return c;
26 }
27
28 public void setC(double c) {
29 this.c = c;
30 }
31
32 sanjiaoxing(double a, double b, double c) {
33 this.a = a;
34 this.b = b;
35 this.c = c;
36 }
37
38 public void getZhouChang() {
39 zhouchang = 0;
40 if ((a + b > c && a + c > b && b + c > a) && (a >= 0 && b >= 0 && c >= 0)) {
41 zhouchang = a + b + c;
42 } else {
43 System.out.println(this.a + "\t" + this.b + "\t" + this.c + "三個數不能構成三角形。");
44 }
45 if (zhouchang != 0) {
46 System.out.println(this.a + "\t" + this.b + "\t" + this.c + "三個數成功構成三角形 ，周長=" + zhouchang);
47 }
48 }
49
50 public static void main(String[] args) {
51 sanjiaoxing s1 = new sanjiaoxing(1.4, 2.5, 3);
52 s1.getZhouChang();
53
54 sanjiaoxing s2 = new sanjiaoxing(1, 3, 4);
55 s2.getZhouChang();
56
57 sanjiaoxing s3 = new sanjiaoxing(1, 5, 5);
58 s3.getZhouChang();
59
60 sanjiaoxing s4 = new sanjiaoxing(3, -4, 5);
61 s4.getZhouChang();
62 }
運行：
