1 /*******************************************************
 2      * Finds and prints n prime integers
 3      * Jeff Offutt, Spring 2003
 4      ******************************************************/
 5     public static void printPrimes (int n)
 6     {
 7         int curPrime; // Value currently considered for primeness
 8         int numPrimes; // Number of primes found so far.
 9         boolean isPrime; // Is curPrime prime?
10         int [] primes = new int [MAXPRIMES]; // The list of prime numbers.
11
12         // Initialize 2 into the list of primes.
13         primes [0] = 2;
14         numPrimes = 1;
15         curPrime = 2;
16         while (numPrimes < n)
17         {
18             curPrime++; // next number to consider ...
19             isPrime = true;
20             for (int i = 0; i <= numPrimes-1; i++)
21             { // for each previous prime.
22                 if (isDivisible(primes[i], curPrime))
23                 { // Found a divisor, curPrime is not prime.
24                     isPrime = false;
25                     break; // out of loop through primes.
26                 }
27             }
28             if (isPrime)
29             { // save it!
30                 primes[numPrimes] = curPrime;
31                 numPrimes++;
32             }
33         } // End while
34
35         // Print all the primes out.
36         for (int i = 0; i <= numPrimes-1; i++)
37         {
38             System.out.println ("Prime: " + primes[i]);
39         }
40     } // end printPrimes

 1 import static org.junit.Assert.*;
 2
 3 import java.io.ByteArrayOutputStream;
 4 import java.io.PrintStream;
 5 import java.lang.reflect.Method;
 6
 7 import org.junit.After;
 8 import org.junit.AfterClass;
 9 import org.junit.Before;
10 import org.junit.BeforeClass;
11
12
13 public class Test {
14     private PrintPrimes p;
15
16     PrintStream console = null;          // 输出流 (字符设备)
17     ByteArrayOutputStream bytes = null;  // 用于缓存console 重定向过来的字符流
18
19     @org.junit.Before
20     public void setUp() throws Exception {
21         p = new PrintPrimes();　　　　　　　　　　　//初始化
22         bytes = new ByteArrayOutputStream();    // 分配空间
23         console = System.out;                   // 获取System.out 输出流的句柄
24         System.setOut(new PrintStream(bytes));  // 将原本输出到控制台Console的字符流 重定向 到 bytes
25     }
26
27     @org.junit.After
28     public void tearDown() throws Exception {
29         System.setOut(console);
30     }
31
32     @org.junit.Test
33     public void testResult() throws Exception {
34         String s = new String("Prime:2" + '\r'+'\n');    // 控制台的换行，这里用 '\r' + '\n' 与println等价
35         s += "Prime:3" + '\r'+'\n';
36         s += "Prime:5" + '\r'+'\n';
37
38         Class pp = p.getClass();
39         //获取方法
40         Method method = pp.getDeclaredMethod("printPrimes",
41                 new Class[]{int.class});
42         //将私有设置可访问
43         method.setAccessible(true);
44         //传值，返回结果对象
45         method.invoke(p, 3);
46 　　　　 //对比结果
47         assertEquals(s, bytes.toString());          // bytes.toString() 作用是将 bytes内容 转换为字符流
48
49     }
50 }