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/**
    知识点: 可变字符串对象 StringBuffer
        1. 什么是StringBuffer
        2. 为什么用StringBuffer
            一般用在很多字符串相连接的情况
        3. StringBuffer的操作和应用
*/
public class TestStringBuffer {
    
    public static void main(String[] args) {
        String str = "";
        //实例化一个空的字符缓冲区
        StringBuffer strBuffer = new StringBuffer();
        for (int i = 0; i < 100; i++) {
            str += i + ",";
            strBuffer.append(i).append(",");
        }
        //输出字符缓冲区的字符串
        System.out.println(strBuffer.toString());

        //1. 字符串追加
        StringBuffer buffer = new StringBuffer();
        buffer.append("How");
        buffer.append(" your");

        //2. 字符串的输出
        System.out.println(buffer.toString());

        //3. 字符串的替换
        buffer.replace(4, 9, "you");
        System.out.println(buffer.toString());

        //4. 字符串插入索引为3的后面
        buffer.insert(3, " are");
        System.out.println(buffer.toString());

        //5. 字符串的截取
        System.out.println(buffer.substring(0, 4));

    }
}

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