StringBuffer和StringBuilder

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class StringBufferDemo {public static void main(String[] args) {StringBuilder sb = new StringBuilder("abcde");int[] arr = {4,1,7,5,9};System.out.println(intToString2(arr));String s1 = "java";String s2 = "hello";show2(s1,s2);System.out.println(s1+"..."+s2);//StringBuffer sb1 = new StringBuffer("java");StringBuffer sb2 = new StringBuffer("hello");show1(sb1,sb2);System.out.println(sb1+"..."+sb2);String str= "abcdef";str = reverse(str,1,4);System.out.println("str="+str);}public static void show2(String s1,String s2){s1.replace('a','n');s1 = s2;}public static void show1(StringBuffer sb1,StringBuffer sb2){sb1.append(sb2);sb2 = sb1;}/*整形数组转成字符串，通过String类。*/public static String intToString(int [] arr){String str = "";for(int x=0; x<arr.length; x++){if(x!=arr.length-1)str = str + arr[x]+ ",";elsestr += arr[x];}return str;}/*整形数组转成字符串，通过StringBuilder类。*/public static String intToString2(int [] arr){StringBuilder sb = new StringBuilder();for(int x=0; x<arr.length; x++){if(x!=arr.length-1)sb.append(arr[x]+ "..");elsesb.append(arr[x]);}return sb.toString();}/*“abcdef”  abedcf将字符串进行部分反转生成新的字符串。是对字符串进行修改。想到了字符串的缓冲区，或者数组。*/public static String reverse(String str,int start,int end){String sub = str.substring(start,end);sub = new StringBuilder(sub).reverse().toString();return new StringBuilder(str).replace(start,end,sub).toString();}}