Guava Preconditions類

Preconditions提供靜態(tài)方法來檢查方法或構(gòu)造函數(shù)，被調(diào)用是否給定適當(dāng)?shù)膮?shù)。它檢查的先決條件。其方法失敗拋出IllegalArgumentException。

類聲明

以下是com.google.common.base.Preconditions類的聲明：

@GwtCompatible
public final class Preconditions
   extends Object

類方法

繼承的方法

這個(gè)類繼承了以下類方法：

• java.lang.Object

Preconditions 示例

使用所選擇的編輯器，創(chuàng)建下面的java程序比如 C:/> Guava

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};
            
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