###for()、增强for()、foreach()、stream().foreach()
*测试一
```java
public class TestFor {
private static void doSome(String s) {
}
public static void main(String[] args) {
/*添加数据*/
List<String> list = new ArrayList<>();
for (int i = 0; i < 10; i++) {
list.add("第" + i + "条数据");
}
/*for循环*/
long st1 = System.currentTimeMillis();
for (int i = 0; i < list.size(); i++) {
doSome(list.get(i));
}
/*增强for循环*/
long st2 = System.currentTimeMillis();
for (String s : list) {
doSome(s);
}
/*foreach*/
long st3 = System.currentTimeMillis();
list.forEach(s -> doSome(s));
/*stream.foreach*/
long st4 = System.currentTimeMillis();
list.stream().forEach(s -> doSome(s));
long st5 = System.currentTimeMillis();
print(st1, st2, st3, st4, st5);
}
/*时间输出*/
public static void print(long s1, long s2, long s3, long s4, long s5) {
System.out.println("for 循环: " + (s2 - s1) + "ms");
System.out.println("增强for 循环: " + (s3 - s2) + "ms");
System.out.println("foreach 循环：" + (s4 - s3) + "ms");
System.out.println("stream.foreach循环：" + (s5 - s4) + "ms");
}
}
```
**结果：**
for 循环: 0ms
增强for 循环: 0ms
foreach 循环：129ms
stream.foreach循环：3ms
------------
* **测试二**
```java
List<String> list = new ArrayList<>();
for (int i = 0; i < 1000; i++) {
list.add("第" + i + "条数据");
}
```
**结果：**
for 循环: 1ms
增强for 循环: 1ms
foreach 循环：121ms
stream.foreach循环：3ms
------------
* **测试三**
```java
List<String> list = new ArrayList<>();
for (int i = 0; i < 1000000; i++) {
list.add("第" + i + "条数据");
}
```
**结果：**
for 循环: 17ms
增强for 循环: 23ms
foreach 循环：165ms
stream.foreach循环：18ms
------------
* **测试四**
```java
private static void doSome(String s) {
try {
Thread.sleep(1);
} catch (InterruptedException e) {
e.printStackTrace();
}
}
```
**结果：**
for 循环: 184ms
增强for 循环: 169ms
foreach 循环：224ms
stream.foreach循环：116ms
网友评论