1, StringBuffer constructor:
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public StringBuffer (): constructor with no arguments
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public StringBuffer (int capacity): Capacity of the specified target string buffer
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public StringBuffer (String str): String buffer object of the specified string content
2, StringBuffer method:
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public int capacity (): returns the current capacity. The theoretical value (do not have)
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public int length (): returns the length (number of characters). The actual value
public class Demo1_StringBuffer {
/**
* * A:StringBuffer的构造方法：
* public StringBuffer():无参构造方法
* public StringBuffer(int capacity):指定容量的字符串缓冲区对象
* public StringBuffer(String str):指定字符串内容的字符串缓冲区对象
* B:StringBuffer的方法：
* public int capacity()：返回当前容量。 理论值(不掌握)
* public int length():返回长度（字符数）。 实际值
* C:案例演示
* 构造方法和长度方法的使用
*/
public static void main(String[] args) {
StringBuffer sb = new StringBuffer();
System.out.println(sb.length()); //容器中的字符个数,实际值
System.out.println(sb.capacity()); //容器的初始容量,理论值
StringBuffer sb2 = new StringBuffer(10);
System.out.println(sb2.length());
System.out.println(sb2.capacity());
StringBuffer sb3 = new StringBuffer("heima");
System.out.println(sb3.length()); //实际字符的个数
System.out.println(sb3.capacity()); //字符串的length + 初始容量
}
}