Java array traversal and summation knowledge points, java array knowledge points

Java array traversal and summation knowledge points, java array knowledge points

One-dimensional array traversal and summation:

Public class OneArry {public static void main (String [] args) {double [] num = {1.9, 2.9, 3.4, 3.5, 10,-1 }; num [0] = new Double (2); // change 1.9 to 2.0 double sum = 0 by subscript; for (int I = 0; I <num. length; I ++) {// traverse System. out. println (num [I]); sum + = num [I]; // sum} System. out. println ("sum of one-dimensional arrays" + sum );}}

Running result:

2.02.93.43.510.0-1.0 the sum of one-dimensional arrays is 20.8.

Two-dimensional array traversal and summation: (method 1)

Public class TwoArry {public static void main (String [] args) {int sum = 0; int num [] [] = {1, 2, 4, 5}, {6, 7, 8, 9, 10}, {11, 12, 13, 14, 15}, {16, 17, 18, 19, 20}, {, 25}; System. out. println ("output two-dimensional array:"); num [0] [0] = new Integer (100 ); // Change 1 in the array to 100 for (int I = 0; I <num. length; I ++) {// traverse, arrange for (int j = 0; j <num [I]. length; j ++) {System. out. print (num [I] [j] + "\ t"); sum + = num [I] [j]; // sum} System. out. println ();} System. out. println ("sum of two-dimensional arrays:" + sum );}}

Running result:

Output two-dimensional array: 1002345678910111213141516171819202122232425 sum of two-dimensional arrays: 424

Two-dimensional array traversal and summation: (method 2)

Public class TwoArry {public static void main (String args []) {int [] [] num = new int [5] [5]; int count = 1; // The array starts from 1 and the int sum = 0; for (int I = 0; I <num. length; I ++) {for (int j = 0; j <num [I]. length; j ++) {num [I] [j] = count ++; // Add count to the array sum + = num [I] [j]; // sum // System. out. println (num [I] [j]); // print all arrays} System. out. println ("sum of two-dimensional arrays:" + sum); System. out. println ("output two-dimensional array:"); for (int I = 0; I <num. length; I ++) {// arrange for (int j = 0; j <num [I]. length; j ++) {System. out. print (num [I] [j] + "\ t");} System. out. println ();}}}

Running result:

Sum of two-dimensional arrays: 325 outputs two-dimensional arrays: 12345678910111213141516171819202122232425

Note: num. length indicates the number of rows, and num. length [I] indicates the number of columns.