摘要：
`import java.util.StringJoiner; public class Demo13{ public static void main(String[] args) { String[] names = {"Bob", "Alice", "Grace"}; //数组元素间用分隔符" 阅读全文
摘要：
`import java.util.StringJoiner; public class Demo12{ public static void main(String[] args) { String[] names = {"Bob", "Alice", "Grace"}; //数组元素间用分隔符" 阅读全文
摘要：
`public class Demo13 { public static void main(String[] args) { String[] fields = { "name", "position", "salary" }; String table = "employee"; String 阅读全文
摘要：
`public class Demo12 { public static void main(String[] args) { String[] fields = { "name", "position", "salary" }; String table = "employee"; String 阅读全文
摘要：
`import java.util.*; public class Demo11{ public static void main(String[] args){ String s1 = "hello"; String s2 = "hELLO".toLowerCase(); String s3 = 阅读全文