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计算数组的L2范数（欧几里德范数或“长度”）。
/* *来 自 N o w J a v a . c o m */ //package com.nowjava; public class Main { public static void main(String[] argv) throws Exception { double[] data = new double[] { 34.45, 35.45, 36.67, 37.78, 37.0000, 37.1234, 67.2344, 68.34534, 69.87700 }; System.out.println(norm(data)); } /** * Computes the L2 norm of an array (Euclidean norm or "length"). */ public static double norm(double[] data) { return (Math.sqrt(sumSquares(data))); } /** * Computes the L2 norm of an array (Euclidean norm or "length"). */ /* from N o w J a v a . c o m */ public static double norm(int[] data) { return (Math.sqrt(sumSquares(data))); } /** * Sums the squares of all components; * also called the energy of the array. */ public static double sumSquares(double[] data) { double ans = 0.0; for (int k = 0; k < data.length; k++) { ans += data[k] * data[k]; } return (ans); } /** * Sums the squares of all components; * also called the energy of the array. */ public static double sumSquares(double[][] data) { double ans = 0.0; for (int k = 0; k < data.length; k++) { for (int l = 0; l < data[k].length; l++) { ans += data[k][l] * data[k][l]; } } return (ans); } /** * Sums the squares of all components; * also called the energy of the array. */ public static int sumSquares(int[] data) { int ans = 0; for (int k = 0; k < data.length; k++) { ans += data[k] * data[k]; } return (ans); }