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Copy pathValidNumber.java
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85 lines (76 loc) · 1.49 KB
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package String;
public class ValidNumber {
boolean parseChar(String s, String c){
char[] cset = c.toCharArray();
for (int i = 0; i < cset.length; i++) {
if (pos < s.length() && cset[i] == s.charAt(pos)) {
pos++;
return true;
}
}
return false;
}
boolean parseSpace(String s) {
for (int i = pos; i <= s.length(); i++) {
if (i == s.length()) {
pos = i;
return true;
}
if (pos< s.length() && s.charAt(i) != ' ') {
pos = i;
return true;
}
}
return false;
}
boolean parseSign(String s) {
if (pos < s.length() && (s.charAt(pos) == '-' || s.charAt(pos) == '+')) {
pos++ ;
return true;
}
return false;
}
boolean parseInt(String s) {
if (parseChar(s, "0123456789")) {
while (parseChar(s, "0123456789"));
return true;
}
return false;
}
boolean parseDoc(String s){
if (pos < s.length() && s.charAt(pos) == '.') {
pos++ ;
return true;
}
return false;
}
boolean parseReal(String s){
boolean f1 = parseInt(s);
boolean f2 = parseDoc(s);
boolean f3 = parseInt(s);
if (f1 || (f2 && f3)) {
return true;
}
return false;
}
int pos = 0;
public boolean isNumber(String s) {
parseSpace(s);
parseSign(s);
if (!parseReal(s)) {
return false;
}
if (parseChar(s, "eE")) {
parseSign(s);
if (!parseInt(s)) {
return false;
}
}
parseSpace(s);
return pos == s.length();
}
public static void main(String[] args) {
String s = "2e10";
System.out.println(new ValidNumber().isNumber(s));
}
}