Java 字符串

String greeting = "Hello";

String txt = "ABCDEFGHIJKLMNOPQRSTUVWXYZ";
System.out.println("The length of the txt string is: " + txt.length());

String txt = "Hello World";
System.out.println(txt.toUpperCase());   // 输出 "HELLO WORLD"
System.out.println(txt.toLowerCase());   // 输出 "hello world"

String txt = "Please locate where 'locate' occurs!";
System.out.println(txt.indexOf("locate")); // 输出 7

String firstName = "John";
String lastName = "Doe";
System.out.println(firstName + " " + lastName);

String firstName = "John ";
String lastName = "Doe";
System.out.println(firstName.concat(lastName));

String txt = "We are the so-called "Vikings" from the north.";

String txt = "We are the so-called \"Vikings\" from the north.";

String txt = "It\'s alright.";

String txt = "The character \\ is called backslash.";

int x = 10;
int y = 20;
int z = x + y;      // z 将为 30（整数/数字）

String x = "10";
String y = "20";
String z = x + y;   // z 将是 1020（一个字符串）

String x = "10";
int y = 20;
String z = x + y;   // z 将是 1020（一个字符串）