How to Use a Switch Case

The switch-case statement in an important tool for cleanly controlling the flow of a program. It functions identically to a long list of \"if then else\" statements, however its more compact and readable structure makes it more suitable when a long list of tests must be performed on a single variable. The switch-case statement will be covered in three major languages: Java, C and Pascal.

Instructions

Java

1. Create the switch statement and open the bracket. The variable being analyzed must be of the int primitive data type. Doubles, floats or other data types cannot be used in a Java switch statement.<br /><br /> switch(x) {

2. Create the conditions and add the break keyword.<br /><br /> case(1):<br /> System.out.print(\"1\")<br />GO<br /> break<br />GO<br /> case(2):<br /> System.out.print(\"2\")<br />GO<br /> break<br />GO<br /><br />Be careful here. Failure to use the break keyword will cause the code to run all the other case instructions until it hits a break. For example, if the break in case(1) is removed and x is equal to 1, then the output will be \"1 2\" rather than simply \"1.\"

3. Create a default condition and close the bracket.<br /><br /> default:<br /> System.out.println(\"Unknown.\")<br />GO<br /> break<br />GO<br /> }<br /><br />The default condition will be run if no other condition matches.

C / C++

1. Create the switch-case statement. It is almost identical to how it appears in Java, except there are no parenthesis surrounding the values being tested for in the case statements.<br /><br />switch(x) {

2. Add the case statements.<br /><br />switch(x) {<br /> case 1:<br /> cout << \"1\"<br />GO<br /> break<br />GO<br /> case 2:<br /> cout << \"2\"<br />GO<br /> break<br />GO<br /> default:<br /> cout << \"Unknown.\"<br />GO<br /> break<br />GO<br /><br /><br /><br />Just like with Java, failure to use the \"break;\" command in C will cause code to be run until one is reached.<br /><br />However, unlike Java, non-integer values, such as characters, can be used in a C/C++ switch-case statement. However, the values being tested for must be expressible as a C constant, so variables cannot be used.

3. Close with a bracket.<br /><br />switch(x) {<br /> case 1:<br /> cout << \"1\"<br />GO<br /> break<br />GO<br /> case 2:<br /> cout << \"2\"<br />GO<br /> break<br />GO<br /> default:<br /> cout << \"Unknown.\"<br />GO<br /> break<br />GO<br />}

Pascal

1. Write the case statement:<br /><br />case x of<br /><br />You should notice that, compared to C and Java, Pascal replaces the \"switch\" keyword with the word \"case.\" It also replaces the \"default\" keyword with the word \"else.\"

2. Add the conditions. <br /><br />case x of<br /> 1: writeln('1')<br />GO<br /> 2: writeln('2')<br />GO<br /> else writeln('Unknown')<br />GO<br /><br />You should also notice that \"break;\" statements are unnecessary in Pascal.

3. Add the end statement. <br /><br />case x of<br /> 1: writeln('1')<br />GO<br /> 2: writeln('2')<br />GO<br /> else writeln('Unknown')<br />GO<br />end<br />GO<br /><br />Unlike Java and C, an \"end\" statement at the end of the whole block of code is needed rather than a closing bracket.

References

• Cplusplus.com: Control Structures
• Sun Microsystems: The Switch Statement
• Free Pascal: The Case Statement