java中如何判断一个字符串是否都为数字 Java中怎样判断一个字符串是否是数字
java\u5982\u4f55\u505a\u5230\u5224\u65ad\u4e00\u4e2a\u5b57\u7b26\u4e32\u662f\u5426\u662f\u6570\u5b57\u3002\u697c\u4e3b\u770b\u65b9\u6cd5:
public class NumberDemo {
public static void main(String[] args) {
String str1="1122.2.2";
String str2="111";
String str3="111.2";
String str4="111s";
String str5="111.s";
String str6="1s11";
System.out.println(str1+":"+isNum(str1));
System.out.println(str2+":"+isNum(str2));
System.out.println(str3+":"+isNum(str3));
System.out.println(str4+":"+isNum(str4));
System.out.println(str5+":"+isNum(str5));
System.out.println(str6+":"+isNum(str6));
}
public static boolean isNum(String str){
return str.matches("^[-+]?(([0-9]+)([.]([0-9]+))?|([.]([0-9]+))?)$");
}
}
\u7ed3\u679c:
1122.2.2:false
111:true
111.2:true
111s:false
111.s:false
1s11:false
\u7528java\u7684\u5f02\u5e38\u673a\u5236\uff0c\u4e0d\u4ec5\u53ef\u4ee5\u5224\u65ad\u662f\u5426\u662f\u6570\u5b57\uff0c\u8fd8\u53ef\u4ee5\u5224\u65ad\u6574\u6570\u6216\u8005\u5c0f\u6570\uff1a
public void checkInt(String bh){
try{
int num = Integer.parseInt(bh);//\u5c06\u8f93\u5165\u7684\u5185\u5bb9\u8f6c\u6362\u6210int
System.out.println("\u662f\u6574\u6570\uff1a"+num);//\u662f\u6574\u6570
}catch (NumberFormatException e) {//\u8f6c\u6362\u6210int\u7c7b\u578b\u65f6\u5931\u8d25
try{
double d =Double.parseDouble(bh);//\u8f6c\u6210double\u7c7b\u578b
System.out.println("\u662f\u5c0f\u6570\uff1a"+d);//\u662f\u5c0f\u6570
}catch (NumberFormatException e2) {//\u8f6c\u6210double\u7c7b\u578b\u5931\u8d25
System.out.println("\u4e0d\u662f\u6570\u5b57");
}
}
}
String str="123";
boolean b=str.matches("[0-9]+");
如果b是false就表示其中含有非数字,如果为true就表示其中全是数字.
+表示匹配1到无穷次.
Pattern pattern = Pattern.compile("[0-9]{1,}");
Matcher matcher = pattern.matcher((CharSequence)str);
boolean result = matcher.matches();
if (result == true) {
System.out.println("yes");
}else{
System.out.println("no");
}
用isNaN函数
if (isNaN('12a2')) alert('不是数字');
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