Java常用实用类（分两次更）

布满荆棘的人生 2022-05-21 07:20 131阅读 0赞

p220

1．public class E {
      public static void main (String args[ ]) {
         String s1,s2,t1="ABCDabcd";
         s1=t1.toUpperCase();
         s2=t1.toLowerCase(); 
         System.out.println(s1);
         System.out.println(s2);
         String s3=s1.concat(s2);
          System.out.println(s3);
       }
    }
    2.   public class E {
      public static void main (String args[ ]) {
         String s="ABCDabcd";
         char cStart=s.charAt(0);
         char cEnd = s.charAt(s.length()-1);
         System.out.println(cStart);
         System.out.println(cEnd);
       }
    }
    3.   import java.util.*;
    public class E {
      public static void main (String args[ ]) {
        int year1,month1,day1,year2,month2,day2;
          try{ year1=Integer.parseInt(args[0]);
               month1=Integer.parseInt(args[1]);
               day1=Integer.parseInt(args[2]);
               year2=Integer.parseInt(args[3]);
               month2=Integer.parseInt(args[4]);
               day2=Integer.parseInt(args[5]);
           }
           catch(NumberFormatException e)
             { year1=2012;
               month1=0;
               day1=1;
               year2=2018;
               month2=0;
               day2=1;
           } 
           Calendar calendar=Calendar.getInstance(); 
           calendar.set(year1,month1-1,day1);  
           long timeYear1=calendar.getTimeInMillis();
           calendar.set(year2,month2-1,day2);  
           long timeYear2=calendar.getTimeInMillis();
           long 相隔天数=Math.abs((timeYear1-timeYear2)/(1000*60*60*24));
           System.out.println(""+year1+"年"+month1+"月"+day1+"日和"+
                                year2+"年"+month2+"月"+day2+"日相隔"+相隔天数+"天");
       }
    }
    4.   import java.util.*;
    public class E {
      public static void main (String args[ ]) {
       double a=0,b=0,c=0;
          a=12;
          b=24;
          c=Math.asin(0.56);
          System.out.println(c);
          c=Math.cos(3.14);
          System.out.println(c);
          c=Math.exp(1);
          System.out.println(c);
          c=Math.log(8);
          System.out.println(c);
       }
    }
    5．public class E {
          public static void main (String args[ ]) {
            String str = "ab123you你是谁？";
            String regex = "\\D+";
            str = str.replaceAll(regex,"");
            System.out.println(str);
          }
    }
    6． import java.util.*;
    public class E {
       public static void main(String args[]) {
          String cost = "数学87分，物理76分，英语96分";
          Scanner scanner = new Scanner(cost);
          scanner.useDelimiter("[^0123456789.]+");
          double sum=0;
          int count =0;
          while(scanner.hasNext()){
             try{  double score = scanner.nextDouble();
                   count++;
                   sum = sum+score;
                   System.out.println(score);
             } 
             catch(InputMismatchException exp){
                  String t = scanner.next();
             }   
          }
          System.out.println("总分:"+sum+"分");
          System.out.println("平均分:"+sum/count+"分");
       }
    }