将数组 int[] arr = {0,1,2,3,4,5,6,7,8,9} 拼接成 [0, 1, 2, 3, 4, 5, 6, 7, 8, 9] 字符串: StringBuilder sb = new StringBuilder(arr.length*3); // StringBuilder(arr.length*3)性能比StringBuilder()高 sb.append("["); // 写法1 for( int i = 0, len = arr.length; ...