String 字符串處理

public class StringConcatTest extends TestCase{
	public static int COUNT = 100000 ;
	public  void testString() {
		String result = "";

		long start = System.currentTimeMillis();
		for (int i = 0; i < COUNT; i++) {
			result = result + i;
		}
		long end = System.currentTimeMillis();
		System.out.println("用 + 耗時：\t" + (end - start));
		
		String result1 = "";
		start = System.currentTimeMillis();
		for (int i = 0; i < COUNT; i++) {
			result1 = result1.concat(String.valueOf(i));
		}
		end = System.currentTimeMillis();
		System.out.println("用 concat 耗時：\t"+(end - start));
		
		start = System.currentTimeMillis();
		StringBuffer buffer = new StringBuffer();
		for (int i = 0; i < 10000; i++) {
			buffer.append(i);
		}
		end = System.currentTimeMillis();
		System.out.println("用 StringBuffer 耗時：\t"+(end - start));
		
		start = System.currentTimeMillis();
		StringBuilder sb = new StringBuilder();
		for (int i = 0; i < 10000; i++) {
			sb.append(i);
		}
		end = System.currentTimeMillis();
		System.out.println("用 StringBuilder 耗時：\t"+(end - start));
	}
}

測試結果

用 + 耗時：	17517
用 concat 耗時：	8813
用 StringBuffer 耗時：	1
用 StringBuilder 耗時：	0