JAVA

Lesson 4: Loops

While Loops

public void alarm() {
    boolen on = checkAlarm();
    if(on){
        beep();
        on=checkAlarm();
    }
    if(on){
        beep();
        on=checkAlarm();
    }
    if(on){
        beep();
        on=checkAlarm();
    }
    ---//until someone turn off the alarm    
}
/*Using While Loop*/
public void alarm(){
    boolean on = checkAlarm();
    while(on){
        beep();
        on = checkalarm();
    }
}
String googol = '1';
int len = googol.length();
while(len <101){
    googol = googol + "0";
    len= googol.length();
}
public void raiseAlarm(int numOfWarnings) {
    int i = 1;
    while(i <= numOfWarnings) {
        System.out.println("warning");
        i++;
    }
    
}

For Loops

public void raiseAlarm(int numOfWarnings) {
    for(int i = 1; i<= numOfWarnings; i++){
        System.out.println("Warning #" + i);
    }
}
/*
Adds the numbers 15+116+ .. + 20
@return the total sum
*/
public int addNmbers() {
    int sum = 0;
    for(int i = 15; i <= 20; i++){
        sum = sum + i;
    }
    return sum;
}
/* Counting Down */
for(int i = 3; i >= 1; i--){
    System.out.println(i);
}
i = i+1 == i++
i = i + 5 == i += 5 
/*Using break;*/
public int martingale() {
 int money = 1000;
 int target = 1200;
 int bet = 10;
 while (money > bet) {
  boolean win = play();
  if (win) {
   money += bet;
   bet = 10;
  } else {
   money -= bet;
   bet *= 2;
  }
  // Add the break here:
  if(money >= target)
     break;
 }
 return money;
}

Arrays

  • cell : value
  • index
int [] numbers = {12,1,777,3,4,0,0,121,1,-4,0,-100,2};
System.out.println(number[0]); // answer is 12
System.out.println()
String [] nesOutlet = {"KBS", "MBC", "SBS", "TVN", "JTBC", "BBC", "FOX", "CNN", "ABC"};
double lucky = Math.random();
//Multiply by 10 to get a fractional number between 0 - 10
luckey *= 10;
//cast to integer to get an integer number between 0 - 9
int luckyIndex = int lucky;
System.out.print(newOutlet[luckyIndex]);

Arrays and Loops

prublic double calculateAverage(double [] temperatures) {
    int size = temperatures.length;
    double total = 0;
for(int i=0; i<size; i++){
    total += temperatures[i];
}
double average = total.size;
return average;
}
/* Array Search - find longest name*/
public String findLongestName(String [] names){
    int size = names.length;
    String longestNames = names[0];
    for(int i=0; i<size; i++){
        if(names[i].length() > longestNames.length()){
            longestNames = names[i];
        }
    }

    return longestNames;
}

2D arrays

public static double englishAverage(int [][] grades, int student) {
    int subjects = grades.length;
    int total = 0;
    for(int i=0;i<subjects;i++) {
        total = grade[i][student];
    }
    double average = total/(double)subjects;
    return average;
}

I’m studing a “Java Programming Basics” @Udacity.

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Eun-young

2019-01-10 13:00

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