JAVA任务一二可以看一下怎样打码

java任务一和任务二，可以看一下解题思路吗，初学有点对java小迷，不知道如何下手

  public static void main(String[] args) {
        String a="I want go outside today";
        String b= a.replace("want go outside","like stay at home");
        String c=b.substring(7,b.length()-6);
        System.out.println(b);//I like stay at home today
        System.out.println(c);//stay at home

        String str2 = "thelaA1mjA1klA2D2A14234A1";
        int index=0,count=0;
       while((index =str2.indexOf("A1",index))!=-1) {
            count++;
           index += 2;
       }
        System.out.println("A1出现"+count+"次");//A1出现4次
     }

public class Basic_18_replaceFirst {
    public static void main(String[] args) {
        String a = "I want go outside today";
        String b = a.replaceFirst("want go outside", "like stay at home");
        String c = b.substring(b.length() - 18, b.length() - 6);
        System.out.println(b);//I like stay at home today
        System.out.println(c);//stay at home

        String str2 = "thelaA1mjA1klA2D2A14234A1";
        int index = 0, count = 0;
        while ((index = str2.indexOf("A1", index)) != -1) {
            count++;
            index += 2;
        }
        System.out.println("A1出现" + count + "次");//A1出现4次
    }
}