Java怎样判断输入是否为数字 java如何循环判断输入是否为数字
java \u600e\u4e48\u5224\u65ad\u63a7\u5236\u53f0\u8f93\u5165 \u662f\u5426\u4e3a\u6570\u5b57\u5927\u81f4\u5982\u4e0b\uff1a\u3000
\u3000import java.util.Scanner;
\u3000\u3000public class testDigit {
\u3000\u3000 public static void main(String[] args) {
\u3000\u3000 Scanner sc = new Scanner(System.in);
\u3000\u3000 String str = sc.nextLine();
\u3000\u3000 while (!(str.matches("\\d+"))) {
\u3000 \u3000System.out.println("\u8f93\u5165\u7684" + str + "\u4e0d\u662f\u6570\u5b57\uff0c\u8bf7\u91cd\u65b0\u8f93\u5165");
\u3000 \u3000str = sc.nextLine();
\u3000 \u3000}
\u3000\u3000System.out.println("\u8f93\u5165\u7684" + str + "\u662f\u6570\u5b57");
\u3000 \u3000}
\u3000\u3000}
\u5475\u5475\uff0c\u8fd9\u4e2a\u95ee\u9898\u95ee\u5f97\u597d\u554a\uff0c\u559c\u6b22\u601d\u8003\u5c31\u597d\uff0c\u5728\u5de5\u4f5c\u4e2d\u6709\u65f6\u5019\u4e5f\u4f1a\u5904\u7406\u4e00\u4e9b\u6570\u636e\uff0c\u50cf\u8fd9\u79cd\u5224\u65ad\u6570\u5b57\u7684\u65b9\u6cd5\u5f88\u5e38\u7528\u3002\u6211\u524d\u51e0\u5929\u5728\u5de5\u4f5c\u4e2d\u5c31\u9047\u5230\u7c7b\u4f3c\u95ee\u9898\uff0c\u6211\u89e3\u51b3\u4e86\uff0c\u5176\u5b9e\u4e5f\u5f88\u7b80\u5355\uff0c\u6211\u4eecjava\u63d0\u4f9b\u4e86\u6b63\u5219\u8868\u8fbe\u5f0f\uff0c\u5982\u679c\u4f60\u60f3\u5230\u8fd9\u70b9\u5c31\u89e3\u51b3\u4e86\uff0c\u6211\u770b\u4e86\u4f60\u7684\u4ee3\u7801\uff0c\u6211\u52a0\u4e86\u70b9\u4e1c\u897f\uff0c\u5df2\u7ecf\u8c03\u8bd5\u6210\u529f\uff0c\u4f60\u5bf9\u6bd4\u770b\u770b\uff0c\u4ee5\u540e\u9047\u5230\u95ee\u9898\u591a\u60f3\u60f3\uff0c\u591a\u95ee\u95ee\u3002
public static void main(String[] args) {
Scanner input=new Scanner(System.in);
int number=-1;//\u5148\u5c06number\u521d\u59cb\u5316
Pattern pattern = Pattern.compile("[0-9]*");//\u9650\u5b9a\u8f93\u5165\u7684\u5fc5\u987b\u662f\u6570\u5b57
do{
System.out.println("1.\u5ba2\u6237\u4fe1\u606f");
System.out.println("2.\u771f\u60c5\u56de\u9988");
System.out.print("\u8bf7\u9009\u62e9\uff1a");
String str=input.nextLine();//\u7528nextLine()\u65b9\u6cd5\u6765\u7edf\u4e00\u63a5\u53d7\uff0c\u8981\u53d6\u5230\u6570\u5b57\u8f6c\u6362\u5c31\u884c\u4e86
if(pattern.matcher(str).matches()){//\u5982\u679c\u8f93\u5165\u7684\u662f\u6570\u5b57\u5c31\u6267\u884c
number=Integer.parseInt(str);
}else{
System.out.println("\u4f60\u8f93\u5165\u7684\u4e0d\u662f\u6570\u5b57\uff0c\u8bf7\u91cd\u65b0\u8f93\u5165...");
}
if(number==1){
System.out.println("\u8fdb\u5165\u5ba2\u6237\u4fe1\u606f");
System.out.println("*******************************************");
}else if(number==2){
System.out.println("\u8fdb\u5165\u771f\u60c5\u56de\u9988");
System.out.println("*******************************************");
}else{
System.out.println("\u8f93\u5165\u9519\u8bef\uff01\u8bf7\u91cd\u65b0\u8f93\u5165\uff01");
System.out.println("*******************************************");
continue;
}
}while(true);
}
以下是个公共类：
public class CharTest {
public CharTest() {
}
public static void main(String args[]) {
String s = "123abc";
for (int i=0;i<s.length();i++) {
char ch = s.charAt(i);
System.out.println(ch + " is digit? " + Character.isDigit(ch));
System.out.println(ch + " is digit? " + (ch >= '0' && ch <= '9'));
}
}
}
以下使用正则表达式来验证
if(str==null || "".equals(str.trim())){
return true;
}
Pattern pattern = Pattern.compile("[0-9]*");
Matcher isNum = pattern.matcher(str.trim());
if(isNum.matches()){
System.out.println("验证为数字");
}else{
System.out.println("验证不是数字");
}
1用JAVA自带的函数publicstaticbooleanisNumeric(Stringstr){for(inti=str.length();--i>=0;){if(!Character.isDigit(str.charAt(i))){returnfalse;}}returntrue;}2用正则表达式publicstaticbooleanisNumeric(Stringst
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绛旓細鏂规硶涓锛氬埄鐢ㄦ鍒欒〃杈惧紡public class Testone {public static void main(String[] args){String str="123456";boolean result=str.matches("[0-9]+");if (result == true) {System.out.println("璇ュ瓧绗︿覆鏄绾鏁板瓧");}else{System.out.println("璇ュ瓧绗︿覆涓嶆槸绾暟瀛");}}}鏂规硶浜岋細鍒╃敤Pattern....
