StringBuffer的解读（二）

最新推荐文章于 2025-09-10 22:21:01 发布

转载最新推荐文章于 2025-09-10 22:21:01 发布 · 69 阅读

0 ·

CC 4.0 BY-SA版权

原文链接：https://yq.aliyun.com/articles/693308

文章标签：

#java

本文深入探讨了StringBuffer在不同场景下的容量调整机制。从默认容量开始，逐步解析append操作如何影响StringBuffer的长度与容量，特别是在超出初始容量及扩容阈值时的行为变化。

StringBuffer的解读（二）

StringBuffer默认容量大小是16个字符。

StringBuffer后面append NULL的测试，代码如下：

public class Test {
    public static void main(String[] args) {
        StringBuffer sb = new StringBuffer("the");
        System.out.println("sb is: " + sb);;
        String str = null;
        sb.append(str);
        System.out.println("sb is: " + sb);;
    }
}

StringBuffer后面append字符串+原先字符数组<容量的测试，代码如下：

public class Test {
    public static void main(String[] args) {
        StringBuffer sb = new StringBuffer("the");
        System.out.println("sb.length: " + sb.length());
        System.out.println("sb.capacity: " + sb.capacity());
        sb.append(" redpig");
        System.out.println("sb.length: " + sb.length());
        System.out.println("sb.capacity: " + sb.capacity());
    }
}

StringBuffer后面append字符串+原先字符数组>容量，且<容量x2+2的测试，代码如下：

public class Test {
    public static void main(String[] args) {
        StringBuffer sb = new StringBuffer("the");
        System.out.println("sb.length: " + sb.length());
        System.out.println("sb.capacity: " + sb.capacity());
        sb.append(" redpig is writting java programs");
        System.out.println("sb.length: " + sb.length());
        System.out.println("sb.capacity: " + sb.capacity());
    }
}

StringBuffer后面append字符串+原先字符数组>容量x2+2的测试，代码如下：

public class Test {
    public static void main(String[] args) {
        StringBuffer sb = new StringBuffer("the");//original length is 3
        System.out.println("sb.length: " + sb.length());
        System.out.println("sb.capacity: " + sb.capacity());
        sb.append(" redpig is writting java programs for fun");//string's length is 33
        System.out.println("sb.length: " + sb.length());
        System.out.println("sb.capacity: " + sb.capacity());
    }
}