J2SE第六章——常用类(二)StringBuffer类

StringBuffer

         问题：String 类是字符数组，长度不变，在执行字符串的连接操作时，是存在问题的

public class Test {
public static void main(String[] args) {
String s1 = "abc";
String s2 = "123";
s1 = s1 + s2;

System.out.println(s1);  // abx123
}
}

解决方法：
       StringBuffer类——长度可以改变的字符串
 
      1.2.1 StringBuffer 构造函数
StringBuffer sb1 = new StringBuffer();
AbstractStringBuffer() {
super(16);
}

AbstractStringBuilder(int capacity) {
value = new char[capacity];
}
StringBuffer sb1 = new StringBuffer(); // new char[16];
-----------------------------------------------------
StringBuffer sb2 = new StringBuffer(20); // new char[20];
------------------------------------------------------
StringBuffer sb3 = new StringBuffer("abc"); // new char[3+16];
}

     1.2.2append() 追加

          ——在原串的尾部追加（影响原字符串）

public class Test {
public static void main(String[] args) {
StringBuffer sb = new StringBuffer("abc");
sb.append("123sgascahrhagad"); // 如果字符数组的长度小于需求，则以16的倍数自动追加
}
}

     1.2.3reverse() 反转

public class Test {
public static void main(String[] args) {
StringBuffer sb = new StringBuffer("abc");
System.out.println(sb.reverse());  // cba
}
}

public class Test {
public static void main(String[] args) {
String s = "Mircosoft";

char[] a = {'a','b','c'};
StringBuffer sb1 = new StringBuffer(S);  // 9+16
sb1.append('/').append("IBM").append('/').append("sun");
System.out.println(sb1);  //     Mircosoft/IBM/sun
}
}