java判断字符串是都全是数字？求一方法 Java中怎样判断一个字符串是否是数字
java\u4e2d\u5224\u65ad\u5b57\u7b26\u4e32\u662f\u5426\u4e3a\u7eaf\u6570\u5b57\u65b9\u6cd5\u4e00\uff1a\u5229\u7528\u6b63\u5219\u8868\u8fbe\u5f0f
public class Testone {
public static void main(String[] args){
String str="123456";
boolean result=str.matches("[0-9]+");
if (result == true) {
System.out.println("\u8be5\u5b57\u7b26\u4e32\u662f\u7eaf\u6570\u5b57");}else{System.out.println("\u8be5\u5b57\u7b26\u4e32\u4e0d\u662f\u7eaf\u6570\u5b57");}}}\u65b9\u6cd5\u4e8c\uff1a\u5229\u7528Pattern.
import java.util.regex.Matcher;
import java.util.regex.Pattern;
public class Testone {
public static void main(String[] args){
String str="123456";
Pattern pattern = Pattern.compile("[0-9]{1,}");
Matcher matcher = pattern.matcher((CharSequence)str);
boolean result=matcher.matches();
System.out.println("\u8be5\u5b57\u7b26\u4e32\u662f\u7eaf\u6570\u5b57");}else{System.out.println("\u8be5\u5b57\u7b26\u4e32\u4e0d\u662f\u7eaf\u6570\u5b57");}}}
ava\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
\u7b2c\u4e00\u3001\u4e09\u79cd\u65b9\u5f0f\u53ea\u80fd\u6821\u9a8c\u4e0d\u542b\u8d1f\u53f7\u201c-\u201d\u7684\u6570\u5b57\uff0c\u5373\u8f93\u5165\u4e00\u4e2a\u8d1f\u6570-199\uff0c\u8f93\u51fa\u7ed3\u679c\u5c06\u662ffalse\uff1b
\u800c\u7b2c\u4e8c\u65b9\u5f0f\u5219\u53ef\u4ee5\u901a\u8fc7\u4fee\u6539\u6b63\u5219\u8868\u8fbe\u5f0f\u5b9e\u73b0\u6821\u9a8c\u8d1f\u6570\uff0c\u5c06\u6b63\u5219\u8868\u8fbe\u5f0f\u4fee\u6539\u4e3a\u201c^-?[0-9]+\u201d\u5373\u53ef\uff0c\u4fee\u6539\u4e3a\u201c-?[0-9]+.?[0-9]+\u201d\u5373\u53ef\u5339\u914d\u6240\u6709\u6570\u5b57\u3002
Scanner sc = new Scanner(System.in);
if(sc.hasNextInt())
{
int a = sc.nextInt();
}
Scanner类的hasNextInt()的这个方法可以做到的。在JAVA的API里找到Scanner类你就知道
你的问题看错了，我这个方法是你输入一串字符，判断它是否是一个数字。解决方法用正则表达式是最方便的。让它去匹配一个表达只有数字的表达式。用String的matches(String str) 这个方法，它返回一个boolean值，str就是一个正则表达式。
下面的例子正负整数，正负小数都能判断
public class Test
{
public static void main(String[] args)
{
String a = "-3439g.434";
String regex = "-?\\d+.\\d+?";
if(a.matches(regex))
System.out.println("是一个数字");
else
System.out.println("不是一个数字");
}
}
用个正则吧：
boolean isAllDigtal(String a){
return a != null && a.matches("[0-9]*");
//如果你认为null是返回true，可以用 return a == null || a.matches("[0-9]*");
}
package test;
public class test {
/**
* @param args
*/
public static void main(String[] args) {
String str = "123232";
System.out.println(check(str));
}
public static boolean check(String str ){
String shuzi = "0123456789";
boolean bool = true ;
char[] strArray = str.toCharArray();
for (int i = 0; i < strArray.length; i++) {
if(!shuzi.contains(String.valueOf(strArray[i]))){
bool = false ;
}
}
return bool ;
}
}
补充 ： 正则验证 适用 正负数
String regex = "^-?[0-9]*$";
System.out.println(str.matches(regex));
用正则表达式吧
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