一文带你掌握Java判断字符串是否为数字的5种实现方法

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();
}

package com.feisuanyz.function;
import com.feisuanyz.flow.core.cmpt.annotation.function.MethodDesc;
import com.feisuanyz.flow.core.cmpt.annotation.function.ParamDesc;
public class StringNumberChecker {
@MethodDesc(desc = "判断字符串是否为数字",
params = {
@ParamDesc(name = "str", desc = "要判断的字符串"),
})
public static boolean isNumeric(String str) {
        if (str == null || str.isEmpty()) { // 检查字符串是否为空
            return false;
        }
        try {
            Double.parseDouble(str); // 使用Double.parseDouble()方法尝试将字符串转换为double
            return true; // 转换成功，字符串是数字
        } catch (NumberFormatException e) {
            return false; // 转换失败，字符串不是数字
        }
    }
}

public final static boolean isNumeric(String s) {
if (s != null && !"".equals(s.trim()))
return s.matches("^[0-9]*$");
else
return false;
}

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;
}

@Test
void judgeStringType()  {
    String s0 = "123";
    String s1 = "adb123";
    String s2 = "-1";
    String s3 = "0";
    String s4 = "3.1415926";
    System.out.println("判断s0是否为数值类型：" + StringUtils.isNumeric(s0)); //true
    System.out.println("判断s1是否为数值类型：" + StringUtils.isNumeric(s1)); //false
    System.out.println("判断s2是否为数值类型：" + StringUtils.isNumeric(s2)); //false
    System.out.println("判断s3是否为数值类型：" + StringUtils.isNumeric(s3)); //true
    System.out.println("判断s4是否为数值类型：" + StringUtils.isNumeric(s4)); //false
}

@Test
void judgeStringType2()  {
    Pattern pattern = Pattern.compile("-?\\d+(\\.\\d+)?");
    String s0 = "123";
    String s1 = "adb123";
    String s2 = "-1";
    String s3 = "0";
    String s4 = "3.1415926";
    System.out.println("判断s0是否为数值类型：" + pattern.matcher(s0).matches()); //true
    System.out.println("判断s1是否为数值类型：" + pattern.matcher(s1).matches()); //false
    System.out.println("判断s2是否为数值类型：" + pattern.matcher(s2).matches()); //true
    System.out.println("判断s3是否为数值类型：" + pattern.matcher(s3).matches()); //true
    System.out.println("判断s4是否为数值类型：" + pattern.matcher(s4).matches()); //true
}