【Java教程】开发中常用记录

所需工具：

Java

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 文章源自灵鲨社区-https://www.0s52.com/bcjc/javajc/13751.html

教程如下

一、编程式事务

1.在执行事务提交或者回滚之前，事务状态不确定时，可以判断一下事务是否已完成，避免重复提交或者回滚出现异常文章源自灵鲨社区-https://www.0s52.com/bcjc/javajc/13751.html

举例：文章源自灵鲨社区-https://www.0s52.com/bcjc/javajc/13751.html

[php]文章源自灵鲨社区-https://www.0s52.com/bcjc/javajc/13751.html

TransactionStatus transactionStatus = platformTransactionManager.getTransaction(transactionDefinition);
if (!transactionStatus.isCompleted()) {
platformTransactionManager.commit(transactionStatus);
}文章源自灵鲨社区-https://www.0s52.com/bcjc/javajc/13751.html

[/php]文章源自灵鲨社区-https://www.0s52.com/bcjc/javajc/13751.html

2.由于编程式事务不会自动提交或者回滚，我们可以在try-catch之后加一个finally，判断事务未完成时，进行回滚，保证每个事务一定会结束

举例：

[php]

TransactionStatus transactionStatus = platformTransactionManager.getTransaction(transactionDefinition);
try {
... ...
} catch (Exception ex) {
... ...
} finally {
if (!transactionStatus.isCompleted()) {
platformTransactionManager.rollback(transactionStatus);
}
}

[/php]

二、Stream

1.使用到的数据结构及模拟数据

[php]

import io.swagger.annotations.ApiModelProperty;
import lombok.Data;
import Java.math.BigDecimal;
@Data
public class Student {
@ApiModelProperty(value = "学生ID")
private String studentId;
@ApiModelProperty(value = "学生姓名")
private String studentName;
@ApiModelProperty(value = "学生性别，1-男，2-女")
private String studentSex;
@ApiModelProperty(value = "学生年龄Integer")
private Integer studentAgeInt;
@ApiModelProperty(value = "学生年龄Double")
private Double studentAgeDou;
@ApiModelProperty(value = "学生年龄BigDecimal")
private BigDecimal studentAgeDec;
}

[/php]

[php]

// 数据列表 List
List<Student> studentList = new ArrayList<>();
Student student = new Student();
student.setStudentId("20220930000001");
student.setStudentName("赵甲");
student.setStudentSex("1");
student.setStudentAgeInt(11);
student.setStudentAgeDou(11.11);
student.setStudentAgeDec(new BigDecimal(11.11));
studentList.add(student);
student = new Student();
student.setStudentId("20220930000002");
student.setStudentName("钱乙");
student.setStudentSex("2");
student.setStudentAgeInt(12);
student.setStudentAgeDou(12.12);
student.setStudentAgeDec(new BigDecimal(12.12));
studentList.add(student);
student = new Student();
student.setStudentId("20220930000003");
student.setStudentName("孙丙");
student.setStudentSex("1");
student.setStudentAgeInt(13);
student.setStudentAgeDou(13.13);
student.setStudentAgeDec(new BigDecimal(13.13));
studentList.add(student);
student = new Student();
student.setStudentId("20220930000004");
student.setStudentName("李丁");
student.setStudentSex("2");
student.setStudentAgeInt(14);
student.setStudentAgeDou(14.14);
student.setStudentAgeDec(new BigDecimal(14.14));
studentList.add(student);
student = new Student();
student.setStudentId("20220930000005");
student.setStudentName("周戊");
student.setStudentSex("1");
student.setStudentAgeInt(15);
student.setStudentAgeDou(15.15);
student.setStudentAgeDec(new BigDecimal(15.15));
studentList.add(student);

[/php]

[php]

// 数据Map
Map<String,Student> studentMap = new HashMap<>(5);
Student student = new Student();
student.setStudentId("20220930000001");
student.setStudentName("赵甲");
student.setStudentSex("1");
student.setStudentAgeInt(11);
student.setStudentAgeDou(11.11);
student.setStudentAgeDec(new BigDecimal(11.11));
studentMap.put(student.getStudentId(),student);
student = new Student();
student.setStudentId("20220930000002");
student.setStudentName("钱乙");
student.setStudentSex("2");
student.setStudentAgeInt(12);
student.setStudentAgeDou(12.12);
student.setStudentAgeDec(new BigDecimal(12.12));
studentMap.put(student.getStudentId(),student);
student = new Student();
student.setStudentId("20220930000003");
student.setStudentName("孙丙");
student.setStudentSex("1");
student.setStudentAgeInt(13);
student.setStudentAgeDou(13.13);
student.setStudentAgeDec(new BigDecimal(13.13));
studentMap.put(student.getStudentId(),student);
student = new Student();
student.setStudentId("20220930000004");
student.setStudentName("李丁");
student.setStudentSex("2");
student.setStudentAgeInt(14);
student.setStudentAgeDou(14.14);
student.setStudentAgeDec(new BigDecimal(14.14));
studentMap.put(student.getStudentId(),student);
student = new Student();
student.setStudentId("20220930000005");
student.setStudentName("周戊");
student.setStudentSex("1");
student.setStudentAgeInt(15);
student.setStudentAgeDou(15.15);
student.setStudentAgeDec(new BigDecimal(15.15));
studentMap.put(student.getStudentId(),student);

[/php]

2.过滤-filter

[php]

// 过滤所有女生
List<Student> studentListT = studentList.stream()
.filter(item -> "2".equals(item.getStudentSex())).collect(Collectors.toList());
// 过滤12岁以上学生（3种数据类型示例）
studentListT = studentList.stream().filter(item -> item.getStudentAgeInt() > 12).collect(Collectors.toList());
studentListT = studentList.stream().filter(item -> item.getStudentAgeDou() > 12).collect(Collectors.toList());
studentListT = studentList.stream()
.filter(item -> item.getStudentAgeDec().compareTo(new BigDecimal(12)) > 0).collect(Collectors.toList());
// 过滤12岁以上男生（2种方法示例）
studentListT = studentList.stream().filter(item -> "1".equals(item.getStudentSex()))
.filter(item -> item.getStudentAgeInt() &amp;gt; 12).collect(Collectors.toList());
studentListT = studentList.stream()
.filter(item -> "1".equals(item.getStudentSex()) &amp;&amp; item.getStudentAgeInt() > 12).collect(Collectors.toList());

[/php]

三、Map转对象

最近，研究map与java对象之间的相互转换，总结了5种方法

https://www.jb51.net/article/190478.htm

四、linux常用命令

1.查看所有java进程

ps -ef | grep java

2.结束某个进程

kill -9 pid