关于字符串连接

对采用+、concat、StringBuffer、StringBuilder的连接效率问题，做了一个简单的测试

public class TestTime {
	public static void main(String[] args) {
		String s = "0";
		long startTime = System.currentTimeMillis();
		for ( int i = 0; i < 50000; i++) {
			s+="0";
		}
		long endTime = System.currentTimeMillis();
		System.out.println("'+'号连接测试(50000个'0'连接)");
		System.out.println((endTime - startTime)+"ms");
//---------------------------------------------------------------------------
		s = "0";
		startTime = System.currentTimeMillis();
		for ( int i = 0; i < 50000; i++) {
			s=s.concat("0");
		}
		endTime = System.currentTimeMillis();
		System.out.println("concat测试(50000个'0'连接)");
		System.out.println((endTime - startTime)+"ms");
//---------------------------------------------------------------------------
		StringBuffer sb = new StringBuffer("0");
		startTime = System.currentTimeMillis();
		for ( int i = 0; i < 5000000; i++) {
			sb.append("0");
		}
		endTime = System.currentTimeMillis();
		System.out.println("StringBuffer连接测试(5000000个'0'连接)");
		System.out.println((endTime - startTime)+"ms");
//---------------------------------------------------------------------------
		StringBuilder sb2 = new StringBuilder("0");
		startTime = System.currentTimeMillis();
		for ( int i = 0; i < 5000000; i++) {
			sb2.append("0");
		}
		endTime = System.currentTimeMillis();
		System.out.println("StringBuiler连接测试(5000000个'0'连接)");
		System.out.println((endTime - startTime)+"ms");
	}
}