找出陣列中最大的元素：

double max = a[0];
for (int i = 1; i < a.length; i++)
    if (a[i] > max) max = a[i];

計算陣列的平均值：

int N = a.length;
double sum = 0.0;
for (int i = 0; i < N; i++)
    sum += a[i];
double average = sum / N; 

複製陣列：

int N = a.length;
double[] b = new double[N];
for (int i = 0; i < N; i++)
    b[i] = a[i];
 

顛倒陣列元素（字串反轉）：

int N = a.length;
for (int i = 0; i < N/2; i++)
{
    double temp = a[i];
    a[i] = a[N-1-i];
    a[N-1-i] = temp;
}

矩陣相乘（方陣），a[ ][ ] *  b[ ][ ] = c[ ][ ]

int N = a.length;
double[][] c = new  double[N][N];
for (int i = 0; i < N; i++)
    for (int j = 0; j < N; j++)
    { //計算行i和列j的點乘
        for (int k = 0; k < N; k++)
            c[i][j] += a[i][j]*b[i][j];
    }