JAVA 判断字符串是否为空的三种方法

Parker — Wed, 24 Mar 2010 15:32:43 +0000

/**
*
* @author USER
* 以下是 Java 判断字符串是否为空的三种方法.
方法一: 最多人使用的一个方法, 直观, 方便, 但效率很低.
方法二: 比较字符串长度, 效率高, 是我知道的最好一个方法.
方法三: Java SE 6.0 才开始提供的方法, 效率和方法二几乎相等, 但出于兼容性考虑, 推荐使用方法二.

以下代码在我机器上的运行结果: (机器性能不一, 仅供参考)
function 1 use time: 141ms
function 2 use time: 46ms
function 3 use time: 47ms
*/
public class CompareStringNothing {
String s = “”;
long n = 10000000;

private void function1() {
long startTime = System.currentTimeMillis();

for(long i = 0; i if(s == null || s.equals(“”));
}
long endTime = System.currentTimeMillis();

System.out.println(“function 1 use time: “+ (endTime – startTime) +”ms”);
}

private void function2() {
long startTime = System.currentTimeMillis();

for(long i = 0; i< n; i++) {
if(s == null || s.length() <= 0);
}
long endTime = System.currentTimeMillis();

System.out.println(“function 2 use time: “+ (endTime – startTime) +”ms”);
}

private void function3() {
long startTime = System.currentTimeMillis();

for(long i = 0; i if(s == null || s.isEmpty());
}
long endTime = System.currentTimeMillis();

System.out.println(“function 3 use time: “+ (endTime – startTime) +”ms”);
}

public static void main(String[] args) {
CompareStringNothing com = new CompareStringNothing();
com.function1();
com.function2();
com.function3();
}
}

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JAVA 判断字符串是否为空的三种方法