YouTipJava Conditional Statements – if…else | Tutorial
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\n\nJava Loop Structures – for, while and do…while
\n\n\nJava Conditional Statements - if...else
\nConditional statements in Java allow a program to execute different blocks of code based on different conditions.
\nAn if statement consists of a boolean expression and one or more statements.
\n\nSyntax
\nThe syntax of an if statement is:
\nif(boolean_expression) {\n /* Executes if the boolean expression is true */\n}If the boolean expression evaluates to true, then the block of code inside the if statement is executed. Otherwise, the code following the else statement block is executed.
\n\nTest.java File Code:
\npublic class Test {\n public static void main(String args[]) {\n int x = 10;\n if( x < 20 ) {\n System.out.print("This is if statement");\n }\n }\n}The compiled and running result of the above code is as follows:
\nThis is if statement\n\n
if...else Statement
\nAn if statement can be followed by an optional else statement, which executes when the boolean expression of the if statement is false.
\n\nSyntax
\nThe usage of if...else is as follows:
\nif(boolean_expression) {\n /* Executes if the boolean expression is true */\n} else {\n /* Executes if the boolean expression is false */\n}Example
\nTest.java File Code:
\npublic class Test {\n public static void main(String args[]) {\n int x = 30;\n if( x < 20 ) {\n System.out.print("This is if statement");\n } else {\n System.out.print("This is else statement");\n }\n }\n}The compiled and running result of the above code is as follows:
\nThis is else statement\n\n
if...else if...else Statement
\nAn if statement can be followed by an optional else if...else statement, which is useful to test multiple conditions.
\nWhen using if, else if, else statements, note the following:
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- An if statement can have zero or one else statement and it must come after any else if statements. \n
- An if statement can have zero to many else if statements and they must come before the else statement. \n
- Once an else if statement evaluates to true, the remaining else if and else statements are skipped. \n
Syntax
\nThe syntax of an if...else if...else statement is:
\nif(boolean_expression 1) {\n /* Executes if the boolean expression 1 is true */\n} else if( boolean_expression 2) {\n /* Executes if the boolean expression 2 is true */\n} else if( boolean_expression 3) {\n /* Executes if the boolean expression 3 is true */\n} else {\n /* Executes if none of the above boolean expressions is true */\n}Example
\nTest.java File Code:
\npublic class Test {\n public static void main(String args[]) {\n int x = 30;\n if( x == 10 ) {\n System.out.print("Value of X is 10");\n } else if( x == 20 ) {\n System.out.print("Value of X is 20");\n } else if( x == 30 ) {\n System.out.print("Value of X is 30");\n } else {\n System.out.print("This is else statement");\n }\n }\n}The compiled and running result of the above code is as follows:
\nValue of X is 30\n\n
Nested if...else Statement
\nIt is legal to nest if-else statements. Which means you can use one if or else if statement inside another if or else if statement.
\n\nSyntax
\nThe syntax for a nested if...else is as follows:
\nif(boolean_expression 1) {\n /* Executes if the boolean expression 1 is true */\n if(boolean_expression 2) {\n /* Executes if the boolean expression 2 is true */\n }\n}You can nest else if...else in the same way as you have nested the if statement.
\n\nExample
\nTest.java File Code:
\npublic class Test {\n public static void main(String args[]) {\n int x = 30;\n int y = 10;\n if( x == 30 ) {\n if( y == 10 ) {\n System.out.print("X = 30 and Y = 10");\n }\n }\n }\n}The compiled and running result of the above code is as follows:
\nX = 30 and Y = 10Java Loop Structures – for, while and do…while
\n\n\n5 Notes Write a Note
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#0 alan.huang
\n407***3@qq.com 74 Using the previously learned variables, for loops, and if knowledge, create a small program. The program's function is to input a diamond shape composed of asterisks (*) in the console. Please see the following code:
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\npublic class Demo2 {\n // Ascending order code below\n public void prit1(float c) {\n float p = c / 2; // Ascending order\n float d; // Declare line number variable\n float e; // Declare asterisk printing variable\n float f; // Declare space printing variable\n float r; // Declare ascending order\n float s = c % 2; // Modulo\n if (s == 0) {\n System.out.println("The data you entered cannot form a diamond structure");\n } else {\n for (d = 1; d <= p; d++) {\n for (f = p; f >= d; f--) {\n System.out.print(" ");\n }\n for (e = 1; e <= d * 2 - 1; e++) {\n if (e == 1 || e == d * 2 - 1) {\n System.out.print("*"); // If it's the first or last number, print *\n } else {\n System.out.print(" "); // Otherwise print a space\n }\n }\n System.out.println();\n }\n }\n }\n\n // Descending order code below\n public void prit2(float m) {\n float i; // Declare line number variable\n float j; // Declare asterisk printing variable\n float k; // Declare space printing variable\n float n = m / 2 + 1; // Descending order\n float o = m % 2; // m modulo\n if (o == 0) {\n System.out.print("");\n } else {\n for (i = 1; i <= n; i++) // Line loop;\n {\n // Print spaces before printing asterisks;\n for (k = 0; k < i - 1; k++) {\n System.out.print(" ");\n }\n // Loop for printing asterisk count below;\n for (j = (n - k) * 2 - 2; j >= 1; j--) // Loop for printing asterisk count;\n {\n if (j == (n - k) * 2 - 2 || j == 1) {\n System.out.print("*");\n } else {\n System.out.print(" ");\n }\n }\n // After printing asterisks, print a newline;\n System.out.println();\n }\n }\n }\n\n public static void main(String[] args) {\n Demo2 a = new Demo2();\n float b = 11; // Based on the number of lines, determine if a diamond can be formed. If it's an odd number of lines, the corresponding diamond can be printed; if it's an even number of lines, output "The data you entered cannot form a diamond structure";\n a.prit1(b);\n a.prit2(b);\n }\n}alan.huang 9 years ago (2017-08-07)
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#0 AntAbu
\n163***4484@qq.com 27 Place the diamond to be printed inside a square. The console prints an a*a area. Find the functions where the diamond's edges are located. Print "*" at points on the edges, and print " " at other points. No need to distinguish between ascending and descending order. Please see the code:
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\npublic class Draw {\n int a, b; // a is the number of rows for the diamond to be generated\n int h; // h is the parameter in the method, also the number of rows\n int i, j; // i j are loop structure parameters\n\n public void draw(int h) {\n for (i = 1; i <= h; i++) { // Print row by row\n for (j = 1; j <= h; j++) { // The number of prints per row is consistent with the row number\n // The statement below is the function for the four edges of the diamond. At coordinate points on the edge, print *, otherwise print a space\n if (j == (h + 3) / 2 - i || j == (h - 1) / 2 + i || j == i - (h - 1) / 2 || j == (3 * h + 1) / 2 - i) {\n System.out.print("*");\n } else {\n System.out.print(" ");\n }\n }\n System.out.println(); // After printing row i, print a newline\n }\n }\n\n public static void main(String[] args) { // Static method\n Draw b = new Draw(); // Initialize method\n int a = 35; // Assign value and execute draw method\n b.draw(a);\n }\n}AntAbu 9 years ago (2017-09-02)
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#0 tf
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