public class homework1 {

    /**
     * @param args
     */
    public static void main(String[] args) {
        // TODO Auto-generated method stub
        String str1="耿丹计算机Java20170320";
        System.out.println(str1.substring(9,17));
    }

}

public class homework2 {

    /**
     * @param args
     */
    public static void main(String[] args) {
        // TODO Auto-generated method stub
        String str="耿丹计算机Java20170320";
        String newStr=str.replaceAll("ava","2EE");
        System.out.println("替换后的结果："+newStr);
    }

}

public class homework3 {

    /**
     * @param args
     */
    public static void main(String[] args) {
        // TODO Auto-generated method stub
        String str="耿丹 计算机 Java 20170320";
        String newStr=str.replaceAll(" ","");
        System.out.println("替换后的结果："+newStr);
    }

}

public class homework4 {

    /**
     * @param args
     */
    public static void main(String[] args) {
        // TODO Auto-generated method stub
        String str="142202199607040111";
        
        System.out.println("此人的生日为：："+str.substring(07,04));
    }

}