Guava:Preconditions检验参数

Guava类库中提供了一个作参数检查的工具类--Preconditions类， 该类可以大大地简化我们代码中对于参数的预判断和处理，让我们对方法输入参数的验证实现起来更加简单优雅，下面我们看看Preconditions类的使用实例：　

import java.util.ArrayList;import java.util.List;import org.junit.Test;import com.google.common.base.Preconditions;public class PreconditionsTest {    @Test  public void Preconditions() throws Exception {         getPersonByPrecondition(8,"peida");        try {      getPersonByPrecondition(-9,"peida");    } catch (Exception e) {      System.out.println(e.getMessage());    }        try {      getPersonByPrecondition(8,"");    } catch (Exception e) {      System.out.println(e.getMessage());    }        try {      getPersonByPrecondition(8,null);    } catch (Exception e) {      System.out.println(e.getMessage());    }        List<Integer> intList=new ArrayList<Integer> ();    for(int i=0;i<10;i++){            try {        checkState(intList,9);        intList.add(i);      } catch (Exception e) {        System.out.println(e.getMessage());      }    }        try {      checkPositionIndex(intList,3);      } catch (Exception e) {      System.out.println(e.getMessage());    }        try {      checkPositionIndex(intList,13);      } catch (Exception e) {      System.out.println(e.getMessage());    }        try {      checkPositionIndexes(intList,3,7);    } catch (Exception e) {      System.out.println(e.getMessage());    }        try {      checkPositionIndexes(intList,3,17);    } catch (Exception e) {      System.out.println(e.getMessage());    }        try {      checkPositionIndexes(intList,13,17);    } catch (Exception e) {      System.out.println(e.getMessage());    }        try {      checkElementIndex(intList,6);    } catch (Exception e) {      System.out.println(e.getMessage());    }        try {      checkElementIndex(intList,16);    } catch (Exception e) {      System.out.println(e.getMessage());    }  }    public static void getPersonByPrecondition(int age,String neme)throws Exception{    Preconditions.checkNotNull(neme, "neme为null");    Preconditions.checkArgument(neme.length()>0, "neme为\'\'");    Preconditions.checkArgument(age>0, "age 必须大于0");    System.out.println("a person age:"+age+",neme:"+neme);       }    public static void checkState(List<Integer> intList,int index)throws Exception{    //表达式为true不抛异常    Preconditions.checkState(intList.size()<index, " intList size 不能大于"+index);  }    public static void checkPositionIndex(List<Integer> intList,int index) throws Exception{    Preconditions.checkPositionIndex(index, intList.size(), "index "+index+" 不在 list中， List size为："+intList.size());  }    public static void checkPositionIndexes(List<Integer> intList,int start,int end) throws Exception{    Preconditions.checkPositionIndexes(start, end, intList.size());  }    public static void checkElementIndex(List<Integer> intList,int index) throws Exception{    Preconditions.checkElementIndex(index, intList.size(),"index 为 "+index+" 不在 list中， List size为： "+intList.size());  }}

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原标题：Guava:Preconditions检验参数

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