Java中判断字符串是否为数字的五种方法

public static boolean isNumeric(String str){
for (int i = str.length();--i>=0;){
if (!Character.isDigit(str.charAt(i))){
return false;
}
}
return true;
}

/*
* 判断是否为整数
* @param str 传入的字符串
* @return 是整数返回true,否则返回false
*/

public static boolean isInteger(String str) {
Pattern pattern = Pattern.compile("^[-\\+]?[\\d]*$");
return pattern.matcher(str).matches();
}

方法三：

<pre name="code" class="java">public static boolean isNumeric(String str){
Pattern pattern = Pattern.compile("[0-9]*");
return pattern.matcher(str).matches();
}<span style="font-family: Helvetica, Tahoma, Arial, sans-serif;"> </span>

方法四：

<pre name="code" class="java">public final static boolean isNumeric(String s) {
<span style="white-space:pre">	</span>if (s != null && !"".equals(s.trim()))
return s.matches("^[0-9]*$");
else
<span style="white-space:pre">	</span>return false;
}

<span style="font-family: Helvetica, Tahoma, Arial, sans-serif;">方法五：用ascii码</span>

<span style="font-family: Helvetica, Tahoma, Arial, sans-serif;"></span><pre name="code" class="java">public static boolean isNumeric(String str){
for(int i=str.length();--i>=0;){
int chr=str.charAt(i);
if(chr<48 || chr>57)
return false;
}
return true;
}

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