正则表达式

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package cn.cccc.demo;
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public class Demo {
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    public static void main(String[] args) {
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       // TODO Auto-generated method stub
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       String str = "123456";
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       if(isNumber(str)){
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           int num = Integer.parseInt(str);
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           System.out.println(num*2);
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       }
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    }
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    public static boolean isNumber(String  str){
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       char data [] = str.toCharArray();
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       for(int x= 0 ; x < data.length ;  x++){
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           if(data[x] > '9' && data[x] <  '0'){
6 collapsed lines
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               return false;
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           }
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       }
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       return true;
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    }
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}

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package cn.cccc.demo;
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public class Demo {
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    public static void main(String[] args) {
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       // TODO Auto-generated method stub
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       String str = "123456";
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       if(str.matches("\\d+")){
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           int num = Integer.parseInt(str);
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           System.out.println(num*2);
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       }
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    }
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}

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package cn.cccc.demo;
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public class Demo {
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    public static void main(String[] args) {
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       // TODO Auto-genera4ted method stub
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       String str =  "1uio4321jd%^sa*4321(sjiod431g541541h431iajj4diud43434321saD";
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       String regex = "[^a-zA-Z0-9]+";
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       System.out.println(str.replaceAll(regex,""));
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    }
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}