Java 字符串 之 字符串StringBuffer

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/**
    知識點: 可變字符串對象 StringBuffer
        1. 什麼是StringBuffer
        2. 爲什麼用StringBuffer
            一般用在很多字符串相連接的情況
        3. StringBuffer的操作和應用
*/
public class TestStringBuffer {
    
    public static void main(String[] args) {
        String str = "";
        //實例化一個空的字符緩衝區
        StringBuffer strBuffer = new StringBuffer();
        for (int i = 0; i < 100; i++) {
            str += i + ",";
            strBuffer.append(i).append(",");
        }
        //輸出字符緩衝區的字符串
        System.out.println(strBuffer.toString());

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

        //2. 字符串的輸出
        System.out.println(buffer.toString());

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

        //4. 字符串插入索引爲3的後面
        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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