Guava教程
Preconditions提供静态方法来检查方法或构造函数,被调用是否给定适当的参数。它检查的先决条件。其方法失败抛出IllegalArgumentException。
以下是com.google.common.base.Preconditions类的声明:
@GwtCompatible
public final class Preconditions
extends Object
类方法
继承的方法
这个类继承了以下类方法: java.lang.Object
使用所选择的编辑器,创建下面的java程序比如 C:/> Guava
GuavaTester.java
import com.google.common.base.Preconditions;
public class GuavaTester {
public static void main(String args[]){
GuavaTester guavaTester = new GuavaTester();
try {
System.out.println(guavaTester.sqrt(-3.0));
}catch(IllegalArgumentException e){
System.out.println(e.getMessage());
}
try {
System.out.println(guavaTester.sum(null,3));
}catch(NullPointerException e){
System.out.println(e.getMessage());
}
try {
System.out.println(guavaTester.getValue(6));
}catch(IndexOutOfBoundsException e){
System.out.println(e.getMessage());
}
}
public double sqrt(double input) throws IllegalArgumentException {
Preconditions.checkArgument(input > 0.0,
"Illegal Argument passed: Negative value %s.", input);
return Math.sqrt(input);
}
public int sum(Integer a, Integer b){
a = Preconditions.checkNotNull(a,
"Illegal Argument passed: First parameter is Null.");
b = Preconditions.checkNotNull(b,
"Illegal Argument passed: Second parameter is Null.");
return a+b;
}
public int getValue(int input){
int[] data = {1,2,3,4,5};
Preconditions.checkElementIndex(input,data.length,
"Illegal Argument passed: Invalid index.");
return 0;
}
}
验证结果
使用javac编译器编译如下类
C:\Guava>javac GuavaTester.java
现在运行GuavaTester看到的结果
C:\Guava>java GuavaTester
看到结果
Illegal Argument passed: Negative value -3.0.
Illegal Argument passed: First parameter is Null.
Illegal Argument passed: Invalid index. (6) must be less than size (5)
转载自并发编程网-ifeve.com