Java开发中常用记录

这篇文章主要介绍了Java-编程式事务、Java-Stream、Linux常用命令,需要的朋友可以参考下

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

举例：

TransactionStatus transactionStatus =  platformTransactionManager.getTransaction(transactionDefinition); if (!transactionStatus.isCompleted()) { platformTransactionManager.commit(transactionStatus); }

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：

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

二、Stream

1.使用到的数据结构及模拟数据

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; }

// 数据列表 List List 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);

// 数据Map Map 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);

2.过滤-filter

// 过滤所有女生 List 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() > 12).collect(Collectors.toList()); studentListT = studentList.stream() .filter(item -> "1".equals(item.getStudentSex()) && item.getStudentAgeInt() > 12).collect(Collectors.toList());