五种Java编程高效编程方法 - Babla

banq

1. 移位操作可以大大提高效率。使用移位操作来计算乐观整数2^n（n是乐观整数）的乘除。
Inefficient code:
int num1 = a * 4; int num2 = a / 4;

Environment friendly code:
int num1 = a << 2; int num2 = a >> 2;

 
2. 类中每个字段变量在每个对象中都有一个复制，而静态固定的每个字段则只有一个。
Inefficient code:
public class HttpConnection {
non-public remaining lengthy timeout = 5L;
...
}

Environment friendly code:
public class HttpConnection {
non-public static remaining lengthy TIMEOUT = 5L;
...
}

 

3.只要您直接分配数据值时，就只要创建一个对象引用直接赋值即可。

Inefficient code:
Lengthy i = new Lengthy(1L);
String s = new String("abc");

Environment friendly code:
Lengthy i = 1L;
String s = "abc";

 
4.在for循环的情况下使用方法调用会浪费资源。
Inefficient code:
Listing<UserDO> userList = ...;
for (int i = 0; i < userList.dimension(); i++) {
...
}

Environment friendly code:
Listing<UserDO> userList = ...;
int userLength = userList.dimension();
for (int i = 0; i < userLength; i++) {
...
}

5. 除非！至关重要，否则不要使用。在non-operator区域会再一次计算

Inefficient code:
if (!(a >= 10)) {
... // Your Code
} else {
... // Your Code
}

Environment friendly code:
if (a < 10) {
... // Your Code
} else {
... // Your Code
}