java中如何判断String中的内容是否为数字？ java判断string是不是数字
java\u4e2d\u5224\u65ad\u5b57\u7b26\u662f\u4e0d\u662f\u6570\u5b57\u95ee\u9898\uff1f\u53c2\u8003\u5982\u4e0b\u4ee3\u7801\u5373\u53ef\u53d1\u73b0\uff1a
public class T { public static void main(String[] args) { System.out.println(isInt("12345")); System.out.println(isInt("abc")); System.out.println(isInt2("12345")); System.out.println(isInt2("abc")); } public static boolean isInt(String string) { return string.matches("\\d+"); } public static boolean isInt2(String string) { try { Integer.parseInt(string); return true; } catch (NumberFormatException e) { return false; } }}
java\u4e2d\u5224\u65ad\u5b57\u7b26\u4e32\u662f\u5426\u4e3a\u6570\u5b57\u7684\u65b9\u6cd5:
1.\u7528JAVA\u81ea\u5e26\u7684\u51fd\u6570
public static boolean isNumeric(String str){
for (int i = 0; i < str.length(); i++){
System.out.println(str.charAt(i));
if (!Character.isDigit(str.charAt(i))){
return false;
}
}
return true;
}
2.\u7528\u6b63\u5219\u8868\u8fbe\u5f0f
\u9996\u5148\u8981import java.util.regex.Pattern \u548c java.util.regex.Matcher
public boolean isNumeric(String str){
Pattern pattern = Pattern.compile("[0-9]*");
Matcher isNum = pattern.matcher(str);
if( !isNum.matches() ){
return false;
}
return true;
}
3.\u4f7f\u7528org.apache.commons.lang
org.apache.commons.lang.StringUtils;
boolean isNunicodeDigits=StringUtils.isNumeric("aaa123456789");
http://jakarta.apache.org/commons/lang/api-release/index.html\u4e0b\u9762\u7684\u89e3\u91ca:
isNumeric
public static boolean isNumeric(String str)Checks if the String contains only unicode digits. A decimal point is not a unicode digit and returns false.
null will return false. An empty String ("") will return true.
StringUtils.isNumeric(null) = false
StringUtils.isNumeric("") = true
StringUtils.isNumeric(" ") = false
StringUtils.isNumeric("123") = true
StringUtils.isNumeric("12 3") = false
StringUtils.isNumeric("ab2c") = false
StringUtils.isNumeric("12-3") = false
StringUtils.isNumeric("12.3") = false
Parameters:
str - the String to check, may be null
Returns:
true if only contains digits, and is non-null
\u4e0a\u9762\u4e09\u79cd\u65b9\u5f0f\u4e2d\uff0c\u7b2c\u4e8c\u79cd\u65b9\u5f0f\u6bd4\u8f83\u7075\u6d3b\u3002
判断字符串是否为数字：
1分解法
public static boolean isNumeric(String str){
for (int i = str.length() ; --i>=0 ; ){
if (!Character.isDigit(str.charAt ( i ) ) ){
return false;
}
}
return true;
}
2>用正则表达式
public static boolean isNumeric(String str){
Pattern pattern = Pattern.compile("[0-9]*");
return pattern.matcher(str).matches();
}
3>用ascii码
public static boolean isNumeric(String str){
for(int i=str.length();--i>=0 {
int chr=str.charAt ;
if(chr<48 || chr>57)
return false;
}
return true;
}
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