Java learning---stage1

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/**compare class String and StringBuilder in time.*/package hellojava;import java.util.*;public class HelloJava {    public static void main(String[] args)     {        String str1="";        ***long  startTime=System.currentTimeMillis();***        for(long i=0;i<10000;i++)        {            ***str1+=i;  //append long i is converted to String***        }        long  endTime=System.currentTimeMillis();        startTime=startTime-endTime;        System.out.println("time consumiton with class Strig"+startTime);        StringBuilder str2=new StringBuilder("");        startTime=System.currentTimeMillis();        for(long i=0;i<10000;i++)        {            ***str2.append(i);  //append,parameter "i"can be any type,eg. long,String etc.***        }        endTime=System.currentTimeMillis();        startTime=startTime-endTime;        System.out.println("time consumiton with class Strig"+startTime);    }}

public static void main(String[] args)     {        String text="小明，叫你回家lol";        ***char[] charArray=text.toCharArray();***        StringBuilder builder=new StringBuilder();        for(int i=0;i<charArray.length;i++)        {            ***builder.append((int)charArray[i]+" ");//paremeter of append can receive any type;here is int and String;***        }        System.out.println("the unicode of the strig is:");        System.out.println(builder.toString());    }

/**判断是否是回文*/public class HelloJava {    public static void main(String[] args)     {        String text="小明，你妈叫你回家吃饭lol";        ***StringBuilder builder=new StringBuilder(text);//将字符串添加到字符串生成器***        ***builder.reverse();//将字符串生成器翻转***        int count=0;        for(int i=0;i<text.length();i++)        {            if(***builder.charAt(i)***!=text.charAt(i))            {                System.out.println("the sentence is not reverse one");                break;            }            else            {                count++;            }        }        if(count==text.length())        System.out.println(" the strig is reverse");    }}

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