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© A+ Computer Science - www.apluscompsci.com
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public class CompSci { } All Java programs start with a class.
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© A+ Computer Science - www.apluscompsci.com public class CompSci { public static void main(String[] args) { System.out.println("Comp Sci!"); } OUTPUT Comp Sci!
![© A+ Computer Science - public class CompSci { public static void main(String[] args) { System.out.println( Comp Sci! ); } OUTPUT Comp Sci!](http://images.slideplayer.com./31/9698690/slides/slide_3.jpg "© A+ Computer Science - public class CompSci { public static void main(String[] args) { System.out.println( Comp Sci! ); } OUTPUT Comp Sci!")
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© A+ Computer Science - www.apluscompsci.com public class CompSci { //open brace public static void main(String[] args) { System.out.println("Comp Sci!"); } } //close brace Braces – You gotta have ‘em! Every class and every method must have a { and a }.
![© A+ Computer Science - public class CompSci { //open brace public static void main(String[] args) { System.out.println( Comp Sci! ); } } //close brace Braces – You gotta have ‘em.](http://images.slideplayer.com./31/9698690/slides/slide_4.jpg "Every class and every method must have a { and a }..")
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© A+ Computer Science - www.apluscompsci.com public class CompSci { public static void main(String[] args) { System.out.println("Comp Sci!"); } You must put a semi-colon at the end of all Java program statements ( ; ).
![© A+ Computer Science - public class CompSci { public static void main(String[] args) { System.out.println( Comp Sci! ); } You must put a semi-colon at the end of all Java program statements ( ; ).](http://images.slideplayer.com./31/9698690/slides/slide_5.jpg "© A+ Computer Science - public class CompSci { public static void main(String[] args) { System.out.println( Comp Sci! ); } You must put a semi-colon at the end of all Java program statements ( ; ).")
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© A+ Computer Science - www.apluscompsci.com Never put a ; before an open { brace ;{ //illegal }; //legal
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© A+ Computer Science - www.apluscompsci.com public class CompSci { public static void main(String[] args) { System.out.println("Comp Sci!"); } Indent all code 3 spaces to make it easier to read.
![© A+ Computer Science - public class CompSci { public static void main(String[] args) { System.out.println( Comp Sci! ); } Indent all code 3 spaces to make it easier to read.](http://images.slideplayer.com./31/9698690/slides/slide_7.jpg "© A+ Computer Science - public class CompSci { public static void main(String[] args) { System.out.println( Comp Sci! ); } Indent all code 3 spaces to make it easier to read.")
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© A+ Computer Science - www.apluscompsci.com
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System.out frequently used methods NameUse print(x)print x and stay on the current line println(x)print x and move to next line down printf(s,x)print x according to s specifications
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© A+ Computer Science - www.apluscompsci.com System.out.print( " compsci"); referencecommand / method OUTPUT compsci
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© A+ Computer Science - www.apluscompsci.com System.out.print("compsci"); OUTPUT compscicompsci
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© A+ Computer Science - www.apluscompsci.com System.out.println("compsci"); OUTPUT compsci
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© A+ Computer Science - www.apluscompsci.com System.out.println("compsci"); OUTPUTcompsci
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© A+ Computer Science - www.apluscompsci.com System.out.println("c\tompsci " ); \nnewline \ttab \rcarriage return \bbackspace OUTPUT c ompsci
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© A+ Computer Science - www.apluscompsci.com System.out.println("com\tpsci " ); OUTPUT com psci \nnewline \ttab \rcarriage return \bbackspace
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© A+ Computer Science - www.apluscompsci.com System.out.println("comp\nsci"); OUTPUT comp sci \nnewline \ttab \rcarriage return \bbackspace
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© A+ Computer Science - www.apluscompsci.com \\outs \ \"outs " \’outs ’ System.out.println( " \\compsci\ " / " ); OUTPUT \compsci"/
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© A+ Computer Science - www.apluscompsci.com \\outs \ \"outs " \’outs ’ System.out.println("\\'comp\'sci\'/"); OUTPUT \'comp'sci'/
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© A+ Computer Science - www.apluscompsci.com Escape Sequences frequently used combinations NameUse \ttabs over five spaces \nmoves to front of next line \bdeletes previous character \rmoves to front of current line \\nets one backslash \ \"nets one double quote " \’nets one single quote ’
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© A+ Computer Science - www.apluscompsci.com //single-line comments /* */block comments //this line prints stuff on the screen System.out.println("stuff");
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© A+ Computer Science - www.apluscompsci.com //single-line comments /* */block comments /* this line prints stuff on the screen */ System.out.println("stuff");
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© A+ Computer Science - www.apluscompsci.com System.out.printf("%s","compsci\n"); OUTPUT compsci
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© A+ Computer Science - www.apluscompsci.com Syntax errors occur when you type something in wrong, causing the code to not compile. //missing semicolon - ; expected System.out.println("stuff") //case problem – should be System system.out.println("stuff")
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© A+ Computer Science - www.apluscompsci.com Runtime errors occur when something goes wrong while the program is running. //an out of bounds exception is thrown String s = "runtime_error"; System.out.println( s.charAt(15) );
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© A+ Computer Science - www.apluscompsci.com
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