Java String

to convert a string, or a portion of a string, into an array of characters

palindrome.getChars(0, len, tempCharArray, 0);

Creating Format Strings

You have seen the use of the printf() and format() methods to print output with formatted numbers. The String class has an equivalent class method, format(), that returns a String object rather than a PrintStream object.

Using String's static format() method allows you to create a formatted string that you can reuse, as opposed to a one-time print statement. For example, instead of

System.out.printf("The value of the float " +
                  "variable is %f, while " +
                  "the value of the " + 
                  "integer variable is %d, " +
                  "and the string is %s", 
                  floatVar, intVar, stringVar);

you can write

String fs;
fs = String.format("The value of the float " +
                   "variable is %f, while " +
                   "the value of the " + 
                   "integer variable is %d, " +
                   " and the string is %s",
                   floatVar, intVar, stringVar);
System.out.println(fs);

« Previous • Trail • Next »

valueOf that converts a string to an object of that type

parseXXXX() that can be used to convert strings to primitive numbers

Since a primitive type is returned instead of an object, the parseFloat() method is more direct than the valueOf() method.

float a = (Float.valueOf(args[0])).floatValue(); // Float a = Float.valueOf(args[0]);
float b = (Float.valueOf(args[1])).floatValue();

float a = Float.parseFloat(args[0]);
float b = Float.parseFloat(args[1]);

3 ways Converting Numbers to Strings

Sometimes you need to convert a number to a string because you need to operate on the value in its string form. There are several easy ways to convert a number to a string:

int i;
// Concatenate "i" with an empty string; conversion is handled for you.
String s1 = "" + i;

// The valueOf class method.
String s2 = String.valueOf(i);

Each of the Number subclasses includes a class method, toString(), that will convert its primitive type to a string. For example:

int i;
double d;
String s3 = Integer.toString(i); 
String s4 = Double.toString(d);

Creating Format Strings

3 ways Converting Numbers to Strings

相关推荐