Common string methods in Java - Step-by-Step Execution

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Concept Flow - Common string methods

Start with a String

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Call method on String

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Method processes String

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Returns result (new String, int, boolean, etc.)

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Use or print result

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End

This flow shows how you start with a string, call a method on it, get a result, and then use that result.

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Execution Sample

Java

String text = "Hello World";
int length = text.length();
String upper = text.toUpperCase();
boolean contains = text.contains("lo");
System.out.println(length);
System.out.println(upper);

This code gets the length of a string, converts it to uppercase, checks if it contains "lo", and prints results.

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Execution Table

Step	Action	Expression	Result	Output
1	Assign string	text = "Hello World"	"Hello World"
2	Get length	text.length()	11
3	Convert to uppercase	text.toUpperCase()	"HELLO WORLD"
4	Check contains substring	text.contains("lo")	true
5	Print length	System.out.println(length)		11
6	Print uppercase	System.out.println(upper)		HELLO WORLD

💡 All methods executed; program ends after printing results.

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Variable Tracker

Variable	Start	After Step 1	After Step 2	After Step 3	After Step 4	Final
text	null	"Hello World"	"Hello World"	"Hello World"	"Hello World"	"Hello World"
length	undefined	undefined	11	11	11	11
upper	undefined	undefined	undefined	"HELLO WORLD"	"HELLO WORLD"	"HELLO WORLD"
contains	undefined	undefined	undefined	true	true	true

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Key Moments - 3 Insights

▶Why does calling toUpperCase() not change the original string?

▶What does length() return exactly?

▶How does contains() work with substrings?

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Visual Quiz - 3 Questions

Look at the execution_table, what is the value of 'length' after step 2?

A 11

B 10

C undefined

D 12

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Concept Snapshot

Common String Methods in Java:
- length() returns number of characters
- toUpperCase() returns uppercase copy
- contains(sub) checks if substring exists
Strings are immutable; methods return new values
Use methods by calling on string variable like text.method()

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Full Transcript

This visual execution shows how common string methods work in Java. We start with a string variable 'text' holding "Hello World". We call length() to get the number of characters, which is 11. Then we call toUpperCase() which returns a new string "HELLO WORLD" without changing the original. Next, contains("lo") checks if "lo" is inside the string and returns true. Finally, we print the length and uppercase string. Variables track these values step-by-step. Key points include that strings do not change when calling methods like toUpperCase(), length counts all characters including spaces, and contains checks for exact substrings. The quiz questions help confirm understanding of these steps.