java中判斷字符串是否是數(shù)字的方法如下：

1、用Java自帶的方法

Java中有一個Character.isDig(char ch)

????public?class?CheckStrIsNum?{???
????????public?static?void?main(String[]?args)?{?????
????????????double?aa?=?-192322.1212;????
????????????String?a?=?"-192322.1212";??
????????????String?b?=?"-192322a1212";?????
????????????String?c?=?"Java";??
????????????String?d?=?"5";????
????????????/**?判斷是否全為數(shù)字?*/?????????????????????
????????????System.out.println(checkStrIsNum01(Double.toString(aa)));????????
????????????System.out.println(checkStrIsNum01(a));????????
????????????System.out.println(checkStrIsNum01(b));????????
????????????System.out.println(checkStrIsNum01(c));????????
????????????System.out.println(checkStrIsNum01(d));?
????????}
????????
????????/**
?????????*?利用Java的character.isDigit方法進(jìn)行處理
?????????*/
????????public?static?boolean?checkStrIsNum01(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;
???????}
????}

顯然b應(yīng)該返回false才對，但是卻返回true，而"5"應(yīng)該返回true，也是結(jié)果錯誤。由此可見，這個結(jié)果，并不完美。

2、利用正則表達(dá)式來判斷

利用正則表達(dá)式來-?[0-9]+(\\.[0-9]+)?來做判斷字符串是否為數(shù)字。
如果傳入的數(shù)據(jù)有很多位，那么使用double會導(dǎo)致精度丟失，這個時候就要用BigDecimal來進(jìn)行轉(zhuǎn)換。

????public?class?CheckStrIsNum?{???
????????public?static?void?main(String[]?args)?{?????
????????????double?aa?=?-192322.1212;????
????????????String?a?=?"-192322.1212";??
????????????String?b?=?"-192322a1212";?????
????????????String?c?=?"Java";??
????????????String?d?=?"5";????
????????????/**?判斷是否全為數(shù)字?*/?????????????????????
????????????System.out.println(checkStrIsNum02(Double.toString(aa)));????????
????????????System.out.println(checkStrIsNum02(a));????????
????????????System.out.println(checkStrIsNum02(b));????????
????????????System.out.println(checkStrIsNum02(c));????????
????????????System.out.println(checkStrIsNum02(d));?
????????}
????????
????????private?static?Pattern?NUMBER_PATTERN?=?Pattern.compile("-?[0-9]+(\\.[0-9]+)?");
????????/**?
?????????*?利用正則表達(dá)式來判斷字符串是否為數(shù)字?
?????????*/
?????????public?static?boolean?checkStrIsNum02(String?str)?{?
????????????String?bigStr;?
????????????try?{??????
????????????????/**?先將str轉(zhuǎn)成BigDecimal，然后在轉(zhuǎn)成String?*/
????????????????bigStr?=?new?BigDecimal(str).toString();?
????????????}?catch?(Exception?e)?{?
????????????????/**?如果轉(zhuǎn)換數(shù)字失敗，說明該str并非全部為數(shù)字?*/
????????????????return?false;?
????????????}?
????????????Matcher?isNum?=?NUMBER_PATTERN.matcher(str);?
????????????if?(!isNum.matches())?{????
????????????????return?false;?
????????????}??
????????????return?true;
????????}
????}

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