Control Flow

# Comparison Operators

int x = 1; 
int y = 1;
boolean equal = (x == y); // true

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# Logical Operators

int temperature = 22;
boolean isWarm = temperature > 20 && temperature < 30; // true
boolean notWarm = temperature < 20 || temperature > 30; // true
boolean warm = !notWarm;

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# If Statements

if (condition_1)
    // blablabla
else if (condition_2)
    // blablabla
else
    // blablabla
    
boolean hasHighIncome = income > 100_000 ? true : false; // ❌
boolean hasHighIncome = income > 100_000; // ✅


// FizzBuzz 
if (isFizz(number) && isBuzz(number))
    sout("FizzBuzz");
else if (isFizz(number)) // even though there is repetition, its more readable and understandable than nested structure
    sout("Fizz");
else if (isBuzz(number))
    sout("Buzz");
else 
    sout(number);

public int isFizz(int number) {
    return number % 5 == 0; 
}

public int isBuzz(int number) {
    return number % 3 == 0; 
}

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# The Ternary Operator

String className = (income > 100_000) ? "high" : "low";

# Switch Statements

switch (role) {
    case "case_1":
        // blablabla
        break;
    case "case_2":
        // blablabla
        break; 
    ...
    default:
        // blablabla
}

// could be number
switch (role) {
    case 1:
        // blablabla
        break;
    case 2:
        // blablabla
        break; 
    ...
    default:
        // blablabla
}

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# For Loops

for (int i = 0; i < something; i++) {
    // blablabla
}

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# While Loops

int i = 100;
while (i > 0) {
    // blablabla
    i --; 
}

// running indefinitely 
Scanner scanner = new Scanner(System.in);
String input = "";
while (!input.equals("quit")) {
    input = scanner.next().toLowerCase();
    sout(input);
}

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# Do..While Loops

Scanner scanner = new Scanner(System.in);
String input = "";

do {
    input = scanner.next().toLowerCase();
    sout(input);
} while (!input.equals("quit"))

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# Break and Continue Statements

Scanner scanner = new Scanner(System.in);
String input = "";
while (true) { // condition can just be true
    input = scanner.next().toLowerCase();
    if (input.equals("quit"))
        break;
    if (input.equals("pass"))
        continue;
    sout(input);
}

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# For-Each Loop

limitations:

always forward going
doesn't has access to index of items

String [] array = {"1", "2", "3"};

for (String number : array)
    sout(number);

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上次更新: 2021/12/31, 15:34:56

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