3-Java logic control statements

table of Contents

Java selection structure

Java loop structure

return、break、continue

1, Java selection structure

1.1, if (condition) ... else structure

- Statement under if executed when the condition == true, otherwise execute statement under else

if(3<=0)
    System.out.println("3<=0");
else
    System.out.println("3>0");

1.2, if (condition 1) ... else if (condition 2) ... else structure

- the next statement if (condition 1) is executed when the condition 1 == true

- Statement under else if (condition n) is executed when the condition n == true

- Statement Under else execute when not satisfied

int e = 3;
int f = 4;
if(e+f>7)
    System.out.println("a");
else if(e+f==7)
    System.out.println("b");
else if(e+f<7)
    System.out.println("c");
else
    System.out.println("d");

1.3, switch (operation statement) ... Case Value Structure

- when the operation result value == case statement, the statement is executed enter the corresponding case

- default: no matter into which case, as long as there is no break, and finally wants to go to default

- break: out of the current selection structure, enter the case if there break, then directly out switch

1.3.1, no default no break

int a = 5
switch(a - 3)

{
case 1:
    System.out.println("one");
case 2:
    System.out.println("two");
case 3:
    System.out.println("three");

1.3.2, there is no break default

int a = 5
switch(a - 3)
{
case 1:
    System.out.println("one");
case 2:
    System.out.println("two");
case 3:
    System.out.println("three");
default:
    System.out.println("default");
}

1.3.3、有default有break

int a = 5
switch(a - 3) {
case 1:
    System.out.println("one");
    break;
case 2:
    System.out.println("two");
    break;
case 3:
    System.out.println("three");
    break;
default:
    System.out.println("default");
}

2、Java循环结构

2.1、while(条件)循环，适用于不清楚循环次数，但知道进入循环的条件时

- 当条件==true时，进入循环

int a = 1;
while(a<=5) {
    System.out.println(a);
    a++;
}

2.2、do…while(条件)循环，适用于不清楚循环次数，但知道停止循环的条件时

- 值型循环中的语句，直到条件==false时，跳出该循环

int b = 1;
do {
    System.out.println(b);
    b++;
}while(b<=5);

2.3、for循环，适用于知道循环的次数的情况

- 格式：for(定义一个变量;条件;运算语句){每次循环要执行的语句}

for(int i=0;i<5;i++) {
    System.out.println(i);
}

3、return、break、continue

- return：跳出当前方法，并返回数据（可以不返回）

- break：跳出当前逻辑结构

- continue：跳出本次循环，执行下一次循环（本次循环中continue后面的代码都不执行）

3-Java logic control statements

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