StringBuffer和StringBuilder

 

//StringBuffer是线程安全的，StringBuilder是线程不安全的

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]+ ",";
			else
				str += 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]+ "..");
			else
				sb.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();
	}
}