在java输出中使用流缓冲区类从字符串中删除子字符串错误验证

在java中使用流缓冲类从字符串中删除子字符串。 输出出错：

请验证此程序

查看我的输出并解释程序的内容？

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所需的输出必须是什么？为了获得正确的输出，必须对程序进行哪些更改

import java.io.*;
public class Strbuff
{
    public static void main(String arg[])throws IOException
    {
        BufferedReader in=new BufferedReader(new InputStreamReader(System.in));
        String str;
        try
        {
            System.out.println("Enter your name");
            str=in.readLine();
            str+="\nThis is example for string Buffer class and its function";
            StringBuffer strbuf=new StringBuffer();
            strbuf.append(str);
            System.out.println(strbuf);
            strbuf.delete(0,str.length());
            strbuf.append("hello");
            strbuf.insert(5,"-java");
            System.out.println(strbuf);
            strbuf.reverse();
            System.out.println("Reversed string");
            System.out.println(strbuf);
            strbuf.reverse();
            System.out.println(strbuf);
            strbuf.setCharAt(5,' ');
            System.out.println(strbuf);
            System.out.println("Character at 6th position");
            System.out.println(strbuf.substring(3,7));
            strbuf.deleteCharAt(3);
            System.out.println(strbuf);
            System.out.println("Capacity of the string Buffer object");
            System.out.println(strbuf.capacity());
            strbuf.delete(6,strbuf.length());
            System.out.println("The string with first 6 letters");
            System.out.println(strbuf);
        }
        catch(StringIndexOutOfBoundsException e)
        {
            System.out.println(e.getMessage());
        }
    }
}

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这是基本的初学者资料，您必须已经涵盖并接触过允许您建立此代码功能的方法。至少你已经获得了执行要求任务所需的阅读材料（或位置）

你所需要做的就是按要求去做。相反，你认为你会来到斯塔奇科弗流，让别人为你做功课，而这不是论坛的目的。我们在这里帮助您克服在成为Java程序员的道路上遇到的绊脚石，但是，您至少必须在遇到绊脚石时表现出一种振作起来的尝试。在这里复制/粘贴你的家庭作业代码并不被认为是一种尝试

逐步浏览每一行代码，并在每一行上放置一条注释，该注释包含该行的简要说明。如果您不知道代码行的作用，那么请阅读您遇到问题的方法。用这种方法尝试不同的事情，在你知道之前，你会对它有一个完整的理解

我将帮助您开始：

// Open a BufferReader InputStream and establish it as variable 'in'... 
BufferedReader in=new BufferedReader(new InputStreamReader(System.in));

// Declare a String variable named 'str'. This string is not originally
//initialized so I'm going to do that now with a Null String...
String str = "";

// Establish a try/catch block to trap a StringIndexOutOfBoundsException
// should it ever occur. This exception is thrown by String methods to
// indicate that an index is either negative or greater than the size of
// the string. For some methods such as the charAt method, this exception
// also is thrown when the index is equal to the size of the string. We
// want to catch this exception so it doesn't crash our program...
try {

    // Print to the display console for User to enter his/her name...
    System.out.println("Enter your name");

    // Read what the User supplied and place the text into our 'str' 
    // String variable...
    str=in.readLine();

    // Add (append) the string "\nThis is example for string Buffer class 
    // and its function" to the 'str' string variable. The '\n' is a output
    // string tag for establishing a new line within the displayed output.
    // the '+=' attached to our 'str' variable is a Assignment Operator. It
    // tells the compiler to adds the right operand to the left operand and
    // assign the result to left operand. It is the same as writing:
    // str = str + "\nThis is example for string Buffer class and its function";
    str+="\nThis is example for string Buffer class and its function";

    // Establish a String Buffer and name it 'strbuf. A StringBuffer is a 
    // thread-safe, mutable sequence of characters. A string buffer is like a 
    // String, but can be modified...
    StringBuffer strbuf=new StringBuffer();

    // Place our current string held within the 'str' string variable into our
    // new String Buffer (strbuf). The StringBuffer.append() method is used for
    // this...
    strbuf.append(str);

    // Print the contents within out string buffer (strbuf) to the display 
    // console...
    System.out.println(strbuf);

    // Now Delete (clear) everything within our String Buffer variable (strbuf).
    // This is done using the StringBuffer.delete() method. 0 indicates the starting
    // point index for the number of characters within the string we want to delete.
    // The 'str.length()' portion indicates the ending index point to delete. The 
    // 'str.length()' method always returns the length of (number of characters) within
    // the string variable (str). So, we know our string variable 'str' contains:
    // the User provided name, let's say: "Vikraman" plus "\nThis is example for string 
    // Buffer class and its function" which in total is 66 characters in length but
    // because indexing always starts from 0 the length of the string (str) is 65. Our
    // line below could be written strbuff.delete(0, 65). Delete characters within the
    // string buffer variable (strbuf) starting from index 0 (the first character) to 
    // index 65 (the last character).
    strbuf.delete(0,str.length());

    ....................................
    ....................................
    ........  You Do The Rest  .........
    ....................................
    ....................................

}
catch(StringIndexOutOfBoundsException e) {
    // Display the exception message to console.
    System.out.println(e.getMessage());
}

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是的……注释过多且过时，但当您完成注释时，您将成为该代码的专业人员。；）

“需要什么样的输出，程序中必须做什么更改才能得到正确的输出？”这是你的程序：我们如何知道你想要它做什么？你期望得到什么输出？实际上，请解释一下这个主题：在java中使用流缓冲类从字符串中删除子字符串，我的o/p与之相关吗？？