java.util.Formatter(File file)文件写不进去数据

本文介绍了一个使用Java的Formatter类向文件写入数据的例子,并强调了必须调用close()方法才能确保数据被正确写入文件。文章通过一个具体的Turtle类实例展示了如何利用Formatter进行输出。

摘要生成于 C知道 ,由 DeepSeek-R1 满血版支持, 前往体验 >

在学习think in java中一个例子中用到Formatter工具类,有看到Formatter(File file)构造方法,猜想应该是将文本写入某个文件中,发现写入不了

最后在stackflow上找到答案了, 需要关闭Formatter对象,才会写入数据

如下

package com.jack.thinkinjava.everythinginobject.string;

import java.io.File;
import java.io.FileNotFoundException;
import java.io.PrintStream;
import java.util.Formatter;

public class Turtle {

	private String name;
	private Formatter f;
	public Turtle(String name, Formatter f){
		this.name = name;
		this.f = f;
	}
	public void move (int x, int y ){
		f.format("%s The Turtle is at (%d, %d)\n", name, x, y);
	}
	
	public static void main(String[] args) throws FileNotFoundException {
		File file = new File("1.txt");
		
		PrintStream outAlias = System.out;
		Formatter f2 = new Formatter(file);
		Turtle tommy = new Turtle("Tommy", f2);
		
		Turtle terry = new Turtle("Terry", new Formatter(outAlias));
		tommy.move(0, 0);
		terry.move(4, 8);
		
		tommy.move(0, 0);
		terry.move(4, 8);
		
		tommy.move(0, 0);
		terry.move(4, 8);
		
		f2.close();
	}
}

f2.close()方法,类似io流 flush()效果

参考地址:https://stackoverflow.com/questions/20036056/formatter-not-writing-to-file

6月 21, 2025 4:40:31 上午 org.apache.coyote.AbstractProtocol init 信息: Initializing ProtocolHandler ["http-bio-8080"] 6月 21, 2025 4:40:31 上午 org.apache.catalina.core.StandardService startInternal 信息: Starting service Tomcat 6月 21, 2025 4:40:31 上午 org.apache.catalina.core.StandardEngine startInternal 信息: Starting Servlet Engine: Apache Tomcat/7.0.47 6月 21, 2025 4:40:32 上午 org.apache.catalina.startup.ContextConfig processAnnotationsJar 严重: Unable to process Jar entry [META-INF/versions/11/module-info.class] from Jar [jar:file:/C:/Users/26945/.m2/repository/com/zaxxer/HikariCP/5.0.1/HikariCP-5.0.1.jar!/] for annotations org.apache.tomcat.util.bcel.classfile.ClassFormatException: Invalid byte tag in constant pool: 19 at org.apache.tomcat.util.bcel.classfile.Constant.readConstant(Constant.java:133) at org.apache.tomcat.util.bcel.classfile.ConstantPool.<init>(ConstantPool.java:60) at org.apache.tomcat.util.bcel.classfile.ClassParser.readConstantPool(ClassParser.java:209) at org.apache.tomcat.util.bcel.classfile.ClassParser.parse(ClassParser.java:119) at org.apache.catalina.startup.ContextConfig.processAnnotationsStream(ContextConfig.java:2134) at org.apache.catalina.startup.ContextConfig.processAnnotationsJar(ContextConfig.java:2010) at org.apache.catalina.startup.ContextConfig.processAnnotationsUrl(ContextConfig.java:1976) at org.apache.catalina.startup.ContextConfig.processAnnotations(ContextConfig.java:1961) at org.apache.catalina.startup.ContextConfig.webConfig(ContextConfig.java:1319) at org.apache.catalina.startup.ContextConfig.configureStart(ContextConfig.java:878) at org.apache.catalina.startup.ContextConfig.lifecycleEvent(ContextConfig.java:376) at org.apache.catalina.util.LifecycleSupport.fireLifecycleEvent(LifecycleSupport.java:119) at org.apache.catalina.util.LifecycleBase.fireLifecycleEvent(LifecycleBase.java:90) at org.apache.catalina.core.StandardContext.startInternal(StandardContext.java:5322) at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:150) at org.apache.catalina.core.ContainerBase$StartChild.call(ContainerBase.java:1559) at org.apache.catalina.core.ContainerBase$StartChild.call(ContainerBase.java:1549) at java.base/java.util.concurrent.FutureTask.run(FutureTask.java:264) at java.base/java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1136) at java.base/java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:635) at java.base/java.lang.Thread.run(Thread.java:840) 6月 21, 2025 4:40:33 上午 org.apache.catalina.core.ApplicationContext log 信息: No Spring WebApplicationInitializer types detected on classpath 6月 21, 2025 4:40:33 上午 org.apache.coyote.AbstractProtocol start 信息: Starting ProtocolHandler ["http-bio-8080"]
最新发布
06-22
评论
添加红包

请填写红包祝福语或标题

红包个数最小为10个

红包金额最低5元

当前余额3.43前往充值 >
需支付:10.00
成就一亿技术人!
领取后你会自动成为博主和红包主的粉丝 规则
hope_wisdom
发出的红包
实付
使用余额支付
点击重新获取
扫码支付
钱包余额 0

抵扣说明:

1.余额是钱包充值的虚拟货币,按照1:1的比例进行支付金额的抵扣。
2.余额无法直接购买下载,可以购买VIP、付费专栏及课程。

余额充值