33. Two-dimensional arrays and the instance variable length

• Statement

  
      int[][] matrix = new int[20][15];
  
  

  declares and instantiates a two-dimensional array matrix of 20 rows and 15 columns

• Each row of matrix is a one-dimensional array:

  
      matrix.length    // returns 20, the number of rows
      matrix[0]        // refers to the first row
      matrix[0].length // returns 15, the number of columns in the first row
      matrix[1].length // returns 15, the number of columns in the second row
      matrix[2].length // and so on.