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| package com.code.note.test;
public class Solution {
public Double parseDouble(String n) {
int isNegative = 1;
String numStr = n.trim();
if (numStr == null) return 0D;
if (numStr.length() > 0 && numStr.charAt(0) == '-') {
isNegative = -1;
numStr = numStr.substring(1);
} else if (numStr.charAt(0) == '+') {
numStr = numStr.substring(1);
}
if (!numStr.contains(".")) {
return (double) getHighPosNum(n);
}
String[] arr = numStr.split("\\.");
double sumHigh = getHighPosNum(arr[0]);
double sumLow = getLowPosNum(arr[1]);
return isNegative * (sumLow + sumHigh);
}
private long getHighPosNum(String highStr1) {
long sumHigh = 0;
String highStr = highStr1;
char[] highChars = highStr.toCharArray();
int[] highIntNums = new int[highChars.length];
for (int i = 0; i < highIntNums.length; i++) {
sumHigh += Math.pow(10, highIntNums.length - 1 - i) * isDigit(highChars[i]);
}
return sumHigh;
}
private int isDigit(char highChar) {
if (!Character.isDigit(highChar)) {
throw new NumberFormatException("非法数字");
}
return (int) highChar - (int) '0';
}
private double getLowPosNum(String lowStr1) {
double sumLow = 0D;
String lowStr = lowStr1;
char[] lowChars = lowStr.toCharArray();
int[] lowIntNums = new int[lowChars.length];
for (int i = 0; i < lowIntNums.length; i++) {
sumLow += Math.pow(10, -1 * (i + 1)) * (isDigit(lowChars[i]));
}
return sumLow;
}
public static void main(String[] args) {
Solution s = new Solution();
double a = s.parseDouble("-1.456");
System.out.println(a);
}
}
|
