public void a() {  
            for (int i = 2; i <= 100; i++) {  
                int temp = (int) Math.sqrt(i);  
                // 我把那个aqrt单独提出来,这样速度稍微快一点,虽然在100内变化不大,但如果是10000000内的素数呢?  
                if (i <= 3) {  
                    System.out.println(i + " is a prime");  
                } else {  
                    for (int j = 2; j <= temp; j++) {// 把Math.sqrt(i)转换为int类形  
                        if (i % j == 0) {  
                            break;  
                        }  
                        if (j >= temp) {  
                            System.out.println(i + " is a prime");  
                        }  
                    }  
      
                }  
            }  
        }  

  public void sushu(int n ,int m){  
            for (int i = n; i < m; i++) {  
                int temp = (int)Math.sqrt(i);  
                if(i<=3){  
                    System.out.println(i);  
                }  
                for (int j = 2; j <= temp; j++) {  
                    if(i%j==0){  
                        break;  
                    }  
                    if(j>=temp){  
                        System.out.println(i);  
                    }  
                }  
            }  
        } 

java求素数算法