Java extracts numbers from a string

1 methods provided by the String class:

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package 测试练习;import Java.util.*;public class get_StringNum {/** *2016.10.25 */public static void main(String[] args) {String str = "love23next234csdn3423javaeye";str=str.trim();String str2="";if(str != null && !"".equals(str)){for(int i=0;i<str.length();i++){if(str.charAt(i)>=48 && str.charAt(i)<=57){str2+=str.charAt(i);}}}System.out.println(str2);}}output:232343423

This method has an obvious disadvantage, can only extract the numbers together, can not be extracted separately. Of course it can be improved, interested friends can try.

2 Regular Expressions

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import java.util.*;import java.util.regex.Matcher;import java.util.regex.Pattern;public class get_StringNum { /** *2016.10.25 */public static void main(String[] args) {String a="love23next234csdn3423javaeye";String regEx="[^0-9]";  Pattern p = Pattern.compile(regEx);  Matcher m = p.matcher(a);  System.out.println( m.replaceAll("").trim());}}output:232343423

Pattern, Matcher is the two classes in the Java.util.regex software package, you can consult the API for specific usage. It is also not possible to extract numbers individually.

3 Collection Class Library

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import java.util.*;import java.util.regex.Matcher;import java.util.regex.Pattern;public class get_StringNum {/** *2016.10.25 */public static void main(String[] args) {  String a="love23next234csdn3423javaeye";List<String> digitList = new ArrayList<String>();Pattern p = Pattern.compile("[^0-9]");Matcher m = p.matcher(a);String result = m.replaceAll("");for (int i = 0; i < result.length(); i++) {digitList.add(result.substring(i, i+1));}System.out.println(digitList);}}output:[2, 3, 2, 3, 4, 3, 4, 2, 3]

The same idea:

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import java.util.*;import java.util.regex.Matcher;import java.util.regex.Pattern;public class get_StringNum {/** *2016.10.25 */public static void main(String[] args) {        String a="love23next234csdn3423javaeye";    List<String> ss = new ArrayList<String>();    for(String sss:s.replaceAll("[^0-9]", ",").split(",")){      if (sss.length()>0)        ss.add(sss);    }    System.out.print(ss);}}output:[2, 3, 2, 3, 4, 3, 4, 2, 3]

Obviously, we can extract the numbers separately using regular expressions.

There is also an answer that is found using the lookup document, as follows:

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/** * 从字符串文本中获得数字 *@param text *@return */ publicstatic List<Long> getDigit(String text) { List<Long> digitList =new ArrayList<Long>(); Pattern p= Pattern.compile("(\\d+)"); Matcher m= p.matcher(text); while (m.find()) { String find= m.group(1).toString(); digitList.add(Long.valueOf(find)); }return digitList; }

Two methods for judging the matching of regular expressions are as follows;

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// 判断一个字符串是否都为数字 public boolean isDigit(String strNum) {   return strNum.matches("[0-9]{1,}"); }  // 判断一个字符串是否都为数字 public boolean isDigit(String strNum) {   Pattern pattern = Pattern.compile("[0-9]{1,}");   Matcher matcher = pattern.matcher((CharSequence) strNum);   return matcher.matches(); }    //截取数字   public String getNumbers(String content) {     Pattern pattern = Pattern.compile("\\d+");     Matcher matcher = pattern.matcher(content);     while (matcher.find()) {       return matcher.group(0);     }     return "";   }  // 截取非数字 public String splitNotNumber(String content) {   Pattern pattern = Pattern.compile("\\D+");   Matcher matcher = pattern.matcher(content);   while (matcher.find()) {     return matcher.group(0);   }   return ""; }

Java extracts numbers from a string