标签：switch 枚举类 java se state his 语句 ++ exit 选择
通过使用条件语句、循环语句可以实现流程的控制。
3.8.1 块作用域（Block Scope）
块（Block）就是由一对花括号包围起来的部分。他指定了一个变量的生存范围，与一个方法的操作范围。 Java中不允许在嵌套块中重复定义变量。
3.8.2 条件语句
if (condition) statement
{ statement 1 statement 2 . . . }
if (yourSales >= target) { performance = "Satisfactory"; bonus = 100 + 0.01 * (yourSales - target); } else { performance = "Unsatisfactory"; bonus = 0; }
if (yourSales >= 2 * target) { performance = "Excellent"; bonus = 1000; } else if (yourSales >= 1.5 * target) { performance = "Fine"; bonus = 500; } else if (yourSales >= target) { performance = "Satisfactory"; bonus = 100; } else { System.out.println("You‘re fired"); }
3.8.3 循环语句
1.while 循环
while (condition) statement
while (balance < goal) { balance += payment; double interest = balance * interestRate / 100; balance += interest; years++; } System.out.println(years + " years.");
2.do-while 循环
do statement while (condition); 注意有；。
do { balance += payment; double interest = balance * interestRate / 100; balance += interest; year++; // print current balance . . . // ask if ready to retire and get input . . . }while (input.equals("N"));
3.8.4 固定次数循环（Determinate loop）
1.for循环
for (int i = 10; i > 0; i--) System.out.println("Counting down . . . " + i);
3.8.5 多重选择 Switch 语句
Scanner in = new Scanner(System.in); System.out.print("Select an option (1, 2, 3, 4) "); int choice = in.nextInt(); switch (choice) { case 1: . . . break; case 2: . . . break; case 3: . . . break; case 4: . . . break; default: // bad input . . . break; }
Case 标签（即Switch后跟的变量类型）可以是：
? char , byte , short , int 及其包装类的常量表达式
? 枚举类型
? 从Java SE 7开始支持string 字面值。
String input = . . .; switch (input.toLowerCase()) { case "yes": // OK since Java SE 7 . . . break; . . . }
3.8.6 跳出循环
1.虽然Java保留的goto关键字，但是不推荐使用goto语句。一般使用break跳出循环。Java支持带标签的break语句，用于跳出多重循环。相当于给每个循环起个名字，跳出时可以指定跳出哪个循环。
label: { . . . if (condition) break label; // exits block . . . } // jumps here when the break statement executes
示例如下：
while (years <= 100) { balance += payment; double interest = balance * interestRate / 100; balance += interest; if (balance >= goal) break; years++; }
Scanner in = new Scanner(System.in); int n; read_data: while (. . .) // this loop statement is tagged with the label { . . . for (. . .) // this inner loop is not labeled { System.out.print("Enter a number >= 0: "); n = in.nextInt(); if (n < 0) // should never happen—can‘t go on break read_data; // break out of read_data loop . . . } }
2.continue 语句
跳出本次循环
CoreJavaE10V1P3.8 第3章 Java的基本编程结构－3.8 控制流程（Control Flow）
标签：switch 枚举类 java se state his 语句 ++ exit 选择
原文地址：http://www.cnblogs.com/imyier/p/6285586.html
