Java从语言层面上来说，if中只能放boolean类型，其他类型都不能通过编译，而从JDK5开始，Java多了自动装...
1//Demonstrate boolean values.2classBoolTest {3publicstaticvoidmain(String args[]) {4booleanb;56b =false;7System.out.println("b is " +b);8b =true;9System.out.println("b is " +b);10//a boolean value can control the if statement11if(b) System.out.println("This is executed.");1...
使用boolean表达式进行条件判断: boolean isTrue = true; boolean isFalse = false; if (isTrue) { System.out.println("This statement is true."); } if (!isFalse) { System.out.println("This statement is also true."); } 复制代码 boolean类型可以作为方法的返回值类型: public boolean isEven(...
// a boolean value can control the if statement if(b) System.out.println("This is executed."); b = false; if(b) System.out.println("This is not executed."); // outcome of a relational operator is a boolean value System.out.println("10 > 9 is " + (...
Statement stmt =conn.createStatement(); ResultSet rs =stmr.executeQuery("select * from Test"); if(rs.next()){ System.out.println("结果集不为空!"); } else{ System.out.println("结果集为空!"); } 1. 2. 3. 4. 5. 6. 7.
if(isTrue){System.out.println("This statement is true!");}if(!isFalse){System.out.println("This statement is also true!");} 1. 2. 3. 4. 5. 6. 7. 在上述代码中,我们使用了if语句来判断布尔变量的值。如果布尔变量的值为true,则执行相应的代码块。
10// a boolean value can control the if statement 11if(b) System.out.println("This is executed.");12 b = false;13if(b) System.out.println("This is not executed.");14// outcome of a relational operator is a boolean value 15 System.out.println("10 > 9 is " + (10 > 9));16...
(); // 检查是否存在结果 boolean exists = resultSet.next(); // 输出结果 if (exists) { System.out.println("值存在于数据库中"); } else { System.out.println("值不存在于数据库中"); } // 关闭连接 resultSet.close(); statement.close(); connection.close(); } catch (SQLException e) ...
booleanvalid=true;if(valid){ <statement>} AI代码助手复制代码 注意: boolean变量只能以true或false作为值。 boolean不能与数字类型相互转换。 包含boolean操作数的表达式只能包含boolean操作数。 Boolean类是boolean原始类型的包装对象类。 2.定义 boolean数据类型。它只有两个值true和false,默认为false。boolean与是否...
In your particular case, your Boolean is null and the if statement triggers an implicit conversion to boolean that produces the NullPointerException 。您可能需要: if(bool != null && bool) { ... } 原文由 K-ballo 发布,翻译遵循 CC BY-SA 3.0 许可协议 有...