一个用不同方法拼接字符串的效率问题。希望大家能看看~~ - 黑马程序员技术交流社区

public class PerformanceTest {
long times;
public PerformanceTest(long times) {
this.times = times;
}
public PerformanceTest start(String title, PerformanceTest.Perform performance) {
long start = System.nanoTime();
for (int i = 0; i < times; i++) {
performance.perform();
}
System.out.println((System.nanoTime() - start) + "(" + title + ")");
return this;
}
protected interface Perform{
public void perform();
}
}

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public class StringConcatTest {
public static void main(String... args) {
new PerformanceTest(1000000).start("用+=", new PerformanceTest.Perform() {
@Override
public void perform() {
concat1("aaaa", "bbbb", "cccc", "dddd", "eeee", "ffff");
}
}).start("用StringBuffer", new PerformanceTest.Perform() {
@Override
public void perform() {
concat2("aaaa", "bbbb", "cccc", "dddd", "eeee", "ffff");
}
}).start("用+", new PerformanceTest.Perform() {
@Override
public void perform() {
concat3("aaaa", "bbbb", "cccc", "dddd", "eeee", "ffff");
}
}).start("用StringBuilder", new PerformanceTest.Perform() {
@Override
public void perform() {
concat4("aaaa", "bbbb", "cccc", "dddd", "eeee", "ffff");
}
});
}
static String concat1(String s1, String s2, String s3, String s4, String s5, String s6){
String result = "";
result += s1;
result += s2;
result += s3;
result += s4;
result += s5;
result += s6;
return result;
}
static String concat2(String s1, String s2, String s3, String s4, String s5, String s6){
StringBuffer buffer = new StringBuffer();
buffer.append(s1).append(s2).append(s3).append(s4).append(s5).append(s6);
return buffer.toString();
}
static String concat3(String s1, String s2, String s3, String s4, String s5, String s6){
return s1 + s2 + s3 + s4 + s5 + s6;
}
static String concat4(String s1, String s2, String s3, String s4, String s5, String s6){
StringBuilder builder = new StringBuilder();
builder.append(s1).append(s2).append(s3).append(s4).append(s5).append(s6);
return builder.toString();
}
}

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