guava学习笔记(1)--参数检验

最新推荐文章于 2024-09-23 15:34:06 发布

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最新推荐文章于 2024-09-23 15:34:06 发布

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分类专栏： Guava 文章标签： guava java

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本文介绍了Guava库中PreCondition类的使用方法，包括参数校验、非空检查等功能，并提供了示例代码。PreCondition有助于提高代码的健壮性和可读性。

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1.PreCondition中提供的参数检验方式，让你的代码变得优雅

PreCondition中的主要方法如下：

Methods
Modifier and Type	Method and Description
`static void`	`checkArgument(boolean expression)` Ensures the truth of an expression involving one or more parameters to the calling method.
`static void`	`checkArgument(boolean expression, Object errorMessage)` Ensures the truth of an expression involving one or more parameters to the calling method.
`static void`	`checkArgument(boolean expression, String errorMessageTemplate, Object... errorMessageArgs)` Ensures the truth of an expression involving one or more parameters to the calling method.
`static int`	`checkElementIndex(int index, int size)` Ensures that `index` specifies a valid element in an array, list or string of size `size`.
`static int`	`checkElementIndex(int index, int size, String desc)` Ensures that `index` specifies a valid element in an array, list or string of size `size`.
`static <T> T`	`checkNotNull(T reference)` Ensures that an object reference passed as a parameter to the calling method is not null.
`static <T> T`	`checkNotNull(T reference, Object errorMessage)` Ensures that an object reference passed as a parameter to the calling method is not null.
`static <T> T`	`checkNotNull(T reference, String errorMessageTemplate, Object... errorMessageArgs)` Ensures that an object reference passed as a parameter to the calling method is not null.
`static int`	`checkPositionIndex(int index, int size)` Ensures that `index` specifies a valid position in an array, list or string of size `size`.
`static int`	`checkPositionIndex(int index, int size, String desc)` Ensures that `index` specifies a valid position in an array, list or string of size `size`.
`static void`	`checkPositionIndexes(int start, int end, int size)` Ensures that `start` and `end` specify a valid positions in an array, list or string of size `size`, and are in order.
`static void`	`checkState(boolean expression)` Ensures the truth of an expression involving the state of the calling instance, but not involving any parameters to the calling method.
`static void`	`checkState(boolean expression, Object errorMessage)` Ensures the truth of an expression involving the state of the calling instance, but not involving any parameters to the calling method.
`static void`	`checkState(boolean expression, String errorMessageTemplate, Object... errorMessageArgs)` Ensures the truth of an expression involving the state of the calling instance, but not involving any parameters to the calling method.

Demo1：

package org.sh.demo01;

import java.util.List;

import org.junit.Test;

import com.google.common.base.Preconditions;



public class GuavaDemo01 {
	@Test
	public void Preconditions(){
		try {
			getObjectPreConditions(8,"suhao");
		} catch (Exception e) {
			System.out.println(e.getMessage());
		}
		try {
			getObjectPreConditions(8,null);
		} catch (Exception e) {
			System.out.println(e.getMessage());
		}
		try {
			getObjectPreConditions(8,"");
		} catch (Exception e) {
			System.out.println(e.getMessage());
		}
		try {
			getObjectPreConditions(-1,"suhao");
		} catch (Exception e) {
			System.out.println(e.getMessage());
		}
	}
	public void getObjectPreConditions(int age ,String name) throws Exception{
		Preconditions.checkNotNull(name,"name must not be null");
		Preconditions.checkArgument(name.length()>0,"name 为\'\'");
		Preconditions.checkArgument(age>0,"age must rl 0");
		System.out.println("name="+name+",age="+age);
	}
}

　Guava的preconditions有这样几个优点:

　　在静态导入后, 方法很明确无歧义, checkNotNull可以清楚地告诉你它是干什么的, 它会抛出怎样的异常.
　　checkNotNull在验证通过后直接返回, 可以这样方便地写代码: this.field = checkNotNull(field).
简单而又强大的可变参数'printf'风格的自定义错误信息.