StringBuffer的append源碼解析（模擬源碼）

package array;

import java.lang.*;

 /**
 * @author wbl
 * 2017-1-6
 * @describe 分析StringBuffer如何append
 */
public class ArrayTest {
   public static void main(String[] args) {
	  StringBuilder sb2 = new StringBuilder("abc");
	  //這一步，源碼AbstractStringBuilder類     value=char[8];count=3;
	  sb2.append("d");
	  //這一步， str.getChars(0, 1, value, 3);  str.getChars(0, len, value, count);
	  //得出 char = abcd

	  char chr1[] = new char[8];
	  chr1[0] = 'a';
	  chr1[1] = 'b';
	  chr1[2] = 'c';
      //getChars(int srcBegin, int srcEnd, char[] dst, int dstBegin)
      String str = "d000";
      str.getChars(0, 1, chr1, 3);
      System.out.print("char = ");
      System.out.print(chr1[0]);
      System.out.print(chr1[1]);
      System.out.print(chr1[2]);
      System.out.println(chr1[3]);
      
      // arraycopy(Object src, int srcPos, Object dest, int destPos, int length)
      //String類getchars方法    arraycopy(value, srcBegin, dst, dstBegin, srcEnd - srcBegin)
      char chr2[] = { 'd'};
    
      System.arraycopy(chr2, 0, chr1, 3, 1);
      System.out.print("array2 = ");
      System.out.print(chr1[0] + " ");
      System.out.print(chr1[1] + " ");
      System.out.print(chr1[2] + " ");
      System.out.print(chr1[3] + " ");
   }
}